Car question

[Clodfobble]

I was thinking I might get a small above-ground pool, fill it with WD-40, and soak the whole car in it. Sure, it would smell funny, but the kids would love sliding off the seats.

[tw]

Originally Posted by Clodfobble

I was thinking I might get a small above-ground pool, fill it with WD-40,

I love the smell of WD-40 - anytime. It also cures bed bug problems.

[classicman]

pssst - UG ... you need new bait? try WD-40 next time.

[Undertoad]

omg don't soak the whole car in wd-40! It just occurred to me that every bolt will loosen simultaneously and the car will fall apart while driving down the highway, like a cartoon!

[tw]

Originally Posted by Undertoad

It just occurred to me that every bolt will loosen simultaneously

But until then, every squeak and rattle will have been eliminated.

[glatt]

Thanks for your input, tw.

FYI, the car is a 4 cylinder.

I was reading the shop manual as I was drifting off to sleep last night. Boy, what an annoying book. You find one list that talks about rough idle possible causes, and each cause sends you to a separate section of the book, so you go to those separate sections, and they each send you to other separate sections, so you spend all your time just flipping around from section to section. I need to just sit down for a couple hours with a notebook and take my own notes from this manual, since trying to find where I read something is pretty much impossible. I've got almost every page in this one section folded over.

Anyway, for the O2 sensor, the voltage ranges are supposed to remain within .1 to .9 volts during operation. It doesn't send you a code until the voltage drops below .05 volts, and in my idle test on my car, it never did.

I also have a few stop and go trips around town recorded, but they are confusing because there is so much variation in road and engine speed. I'll try to fit in a short trip on the highway this weekend.

One amusing thing is that this CarChip Pro is also marketed as a way to snoop on your teenage driver and tell you if they accelerate too fast or stop too fast. My wife never triggered the thing, but almost every time I stop when driving, I set the damn thing off. So I come to a stop at a stop sign and the damn thing beeps at me. Then I stop at a red light, and it beeps again. I'm not jamming on the brakes. Honest. But my wife thinks it's funny. There's some way to turn it off, but I haven't figured it out, and maybe it will make me into a "better" driver.

[Clodfobble]

Like the giant lego ball!

[glatt]

[Clodfobble]

There was a review on the Amazon page by a dad who had purchased it to monitor his son's driving habits... and when his son got a ticket for going 90 in a 55, the son swore he wasn't going that fast, and the dad's all, "Yeah yeah, sure son. Let's check the record, shall we?" And it turned out, no, the CarChipPro had recorded a speed of only 62 at that time. Still speeding, of course, but obviously not 90. They presented the data in court and got the ticket thrown out.

[infinite monkey]

Originally Posted by Clodfobble

There was a review on the Amazon page by a dad who had purchased it to monitor his son's driving habits... and when his son got a ticket for going 90 in a 55, the son swore he wasn't going that fast, and the dad's all, "Yeah yeah, sure son. Let's check the record, shall we?" And it turned out, no, the CarChipPro had recorded a speed of only 62 at that time. Still speeding, of course, but obviously not 90. They presented the data in court and got the ticket thrown out.

Nice! I like!

[glatt]

A year and 150 posts ago, I complained in this thread about a rough idle my car has. If you are a glutton for punishment, you can go back and re-read it all, starting at post 55. The problem is still there.

The executive summary is that after driving the car for a while and the engine gets warm, I stop at a light and put the car in neutral or step on the clutch, and it begins to idle. And vibrate. A lot. It's annoying. It's loud. It didn't use to be like that. It used to be smooth and quiet. Now it's rough and loud and vibrating. However, the fuel economy is as good as ever. I got 39.5 mpg on the highway on a trip back from Maine over the summer. Very pleased with that. Normally it's city driving and around 30.

We recently bought a second car, which means I can take a day here and there to work on this one, and the other one is available for use. No pressure to get it fixed in a half hour window before the next soccer game. So I am returning my attention to this problem.

So far, I've tested the engine mounts by putting on the parking brake and trying to drive forward and reverse while watching the engine. The engine barely moves. I think the mounts are good. I ran a few bottles of fuel injection cleaner through the gas tank according to instructions. No change. I paid the corner mechanic to clean the throttle body when they were doing an oil change. No change. But I recently took the air filter off to check the throttle body, and noted that it was clean, so they did the work. I tried to clean the mass airflow sensor, but discovered that this car (1996 Geo Prizm) does not have one. It has a pressure sensor instead and I understand you don't clean those.

Here's the throttle body.

Looks clean to me. The little square-ish hole at the bottom of the throttle leads down to the Idle Air Control valve. It looks like it might be a little dirty down there, so I may try cleaning that next. It's kind of complicated though. I'd need to remove a few hoses, including coolant lines, some data cables, and a throttle cable before I can get the throttle body off, and then take the IAC off of the throttle body and clean it out. Maybe this weekend. Seems like if I'm having idle trouble, the problem might be the idle control valve.

How do you take off a couple of coolant hoses without getting coolant everywhere or bubbles in the coolant system? Do I need to flush or bleed the coolant afterwards? Sounds like a lot to go through to clean something in the hopes it will fix the problem.

[tw]

I would not waste time cleaning things. Cleaning rarely fixes such obvious problems. And might even create more problems if disconnecting the coolant is necessary.

If I remember correctly, we went through a list of suspects from the manual and other suggestions. Eliminating many including fuel and O2 Sensor. Mileage and operation when not in idel mode eliminates most suspects (including motor mounts). Listen to the exhaust pipe both on idle cold and idle hot. Any missing that corresponds to the roughness?

When cold, the idle is probably faster. Might not feel rough. A problem not apparent in cold (faster) idle might still exist and be heard in the exhaust pipe. Missing in the exhaust pipe would eliminate motor mounts and other static reasons for roughness.

Does the roughness appear suddenly or gently become obvious as idle RPMs slowly decrease?

Does this fuel injection system do a fast idle by holding the throttle plate slightly open or by opening a fast idle air valve (not to be confused with the Idle Air Control valve)? IOW is there a relay or vacuum line that partially holds the throttle open for a fast idle?

As noted previously, an idle control system operates different from high speed operation. Parts that are common to both operations (ie spark system) can be eliminated since they work fine in high speed operation. Apparently performance and gas mileage say all high speed subsystems work OK.

Some previous questions I don't recall seeing answered. How does this car perform timing? For example, does the distributor have vacuum and centrifical advance and retard to mechanically adjust when spark plugs fire? Or is engine timing done electronically? Carchip may report timing as the engine gets warmer.

One part that operates only in idle mode (not in high speed mode) is the Idle control valve. A binding valve might explain rough idle. However, if difficult to access, then better is to eliminate other possible suspects first.

EGR valve can be in that suspect list. EGR valve is open during high speed operation. But must fully seal always during idle. That valve leaking exhuast gas during idle means it too would be a part that could only affect low RPM idle. And is often easily tested. Two reasons for that leaking would be vacuum on that EGR valve at idle (when no vacuum should be opening that valve) or the valve does not fully seat (close) at hot idle. The later can only be confirmed by temporary removal and inspection. Former becomes obvious by disconnecting an EGR controlling vacuum line and covering that hose with a finger. No vacuum should exist during idle.

I don't remember the long list of suspects. Don't remember any error codes. And don't remember why we spent so much time eliminating an O2 Sensor and gasoline from the suspect list. But gas mileage and high speed performance also eliminate both from the suspect list.

[glatt]

Originally Posted by tw

I would not waste time cleaning things. Cleaning rarely fixes such obvious problems. And might even create more problems if disconnecting the coolant is necessary.

If I remember correctly, we went through a list of suspects from the manual and other suggestions. Eliminating many including fuel and O2 Sensor. Mileage and operation when not in idel mode eliminates most suspects (including motor mounts). Listen to the exhaust pipe both on idle cold and idle hot. Any missing that corresponds to the roughness?

When cold, the idle is probably faster. Might not feel rough. A problem not apparent in cold (faster) idle might still exist and be heard in the exhaust pipe. Missing in the exhaust pipe would eliminate motor mounts and other static reasons for roughness.

Does the roughness appear suddenly or gently become obvious as idle RPMs slowly decrease?

Does this fuel injection system do a fast idle by holding the throttle plate slightly open or by opening a fast idle air valve (not to be confused with the Idle Air Control valve)? IOW is there a relay or vacuum line that partially holds the throttle open for a fast idle?

As noted previously, an idle control system operates different from high speed operation. Parts that are common to both operations (ie spark system) can be eliminated since they work fine in high speed operation. Apparently performance and gas mileage say all high speed subsystems work OK.

Some previous questions I don't recall seeing answered. How does this car perform timing? For example, does the distributor have vacuum and centrifical advance and retard to mechanically adjust when spark plugs fire? Or is engine timing done electronically? Carchip may report timing as the engine gets warmer.

One part that operates only in idle mode (not in high speed mode) is the Idle control valve. A binding valve might explain rough idle. However, if difficult to access, then better is to eliminate other possible suspects first.

EGR valve can be in that suspect list. EGR valve is open during high speed operation. But must fully seal always during idle. That valve leaking exhuast gas during idle means it too would be a part that could only affect low RPM idle. And is often easily tested. Two reasons for that leaking would be vacuum on that EGR valve at idle (when no vacuum should be opening that valve) or the valve does not fully seat (close) at hot idle. The later can only be confirmed by temporary removal and inspection. Former becomes obvious by disconnecting an EGR controlling vacuum line and covering that hose with a finger. No vacuum should exist during idle.

I don't remember the long list of suspects. Don't remember any error codes. And don't remember why we spent so much time eliminating an O2 Sensor and gasoline from the suspect list. But gas mileage and high speed performance also eliminate both from the suspect list.

Thanks for the post! I'm not excited about removing and cleaning the IAC valve because I don't want to mess with the coolant unless I have to. I just read the section of the manual that talks about this, and the second step after relieving fuel pressure is to drain the coolant system. What a job!

A little more information:

1. I've only been using name brand fuel (Shell) for the last year.

2. Car has an O2 sensor next to the exhaust manifold by the engine, and one after the cat under the car. I've looked at the charts from the carchip pro, but don't really know how to interpret them. One potentially interesting thing that I noticed this weekend is that the outer protecting sleeve of the wires going the the first O2 sensor by the manifold is all chewed up and torn. There had been a cable tie holding that sleeve to a coolant hose away from the fan, and the cable tie was broken and slipped down the coolant tube. The O2 wire harness was hanging loosely between the fan and the exhaust manifold. But when I inspected the wires within that damaged sleeve, the insulation on the wires was undamaged, and the sensor sends readings to the carchip pro. So I assume it is fine, even though it looks like hell.

3. No error codes.

4. I think the timing is controlled by the computer. And I just confirmed. Manual says "All spark timing changes in the distributor are performed electronically by the Engine Control Module Powertrain Control Module." The OBD2 system will send data to the Carchip for "timing advance." But I don't know what those numbers mean.

5. Roughness is not present at cold start up, but I wouldn't say the engine is smooth either. The problem may exist when cold. Hard to tell. It gradually gets worse as the car warms up and the RPMs drop a little, but then suddenly gets a lot worse. I assume this abrupt change happens at the point when the car decides it's warm and changes from rich to lean mode.

6. There is a throttle opener that increases idle speed during start up conditions. A vacuum hose goes from the top of the throttle body to the throttle opener and appears to be what activates the throttle opener. I haven't studied this during a warm idle, so I don't know if it does anything after the engine has warmed up. The manual discusses ways to test this throttle opener, but it requires a real time scan tool to monitor RPM while you fiddle with the hoses at a specific RPM and then confirm that the engine drops to another RPM when you let go of the throttle with the hose plugged. I don't own a real time scan tool that will display RPM, so I can't test this component right now.

I am intrigued by the EGR. It looks easier to test than the IAC. I think I'll focus on that this weekend instead.

Also, listening at the exhaust pipe sounds easy. Could you describe in more detail what I should be listening for?

[BigV]

Hey xoB

A war of words here is battling on his turf. Here are some pictures that might help.

I've been following along, silently . I see a bit of which will naturally progress to and . That's great if you want to descend to his level. Personally, I think this is . All the in the world won't transform a into . Old and busted--. New hotness--

Just my

[glatt]

Yeah, so anyway, I've got a 4 day weekend coming. I should have some time in there to tinker a little.

My plan is to double check the engine mounts using a mirror and flashlight to really examine them. I had done the "see if the engine moves around under load" test, and ruled them out, but they are the most obvious culprit so I'm going to try to really get a good look at them.

Then I'm going to spray a bunch of carb cleaner on the vacuum hoses to check for a leak, since that's probably the next most likely culprit.

And then I'm going to look for anything that's touching the frame/body that shouldn't be.

Wish I had some jack stands. I asked for some for Christmas, so can't go out and buy any yet. It would be a lot easier to examine this car if I could raise it a bit and get under it safely.