Bonnie shudders and dies...a lot.

[tannerr52]

OK so my next new dilemma. I drive a 1990 Pontiac Bonneville. lately it has been having some issues. Mind you, this is an off and on thing. When I start the car rough (taking more than 5 seconds to crank), then it runs rough. Shut the car off, let it sit for awhile, and then start it again(lets say it starts within 2 seconds), and it runs just fine. So when it does run rough, if you are stopped, in park, the car idles below 500 RPM, which is 500 RPM, well, too low. When going any speed over 25 or so, and take your foot off the gas, the cars idle bounces between 550 and 900 RPM, give or take. The service light is on and i have also came up with 2 errors, Torque Converter Clutch error, and Cam sensor error. I have tested the fuel pressure and it is normal. I have replaced the Cam sensor and that has done nothing. I put some Sea Foam Trans Tube in the tranny, to try to free up any TCC solenoids, and still nothing. I've wiggled every single wire and connector, and unplugged the battery to try to reset the ECM, still nothing. The car has a new starter too, btw. And when it does start rough, which is about all the time, you get a very bad exhaust/gas smell. I believe that this is a separate issue that needs fixed, as well.

Any help would be greatly appreciated, I don't have a ton of money to shell out on a mechanic. (Don't we all?)
Thanks,
Tanner

[shorod]

Have you tried posting in the Bonneville forum? If you need help moving this thread to that forum, let me know.

When's the last time the car had a tune up (including spark plugs, plug wires, and fuel filter)? Yeah, it seems a bit odd that if the car starts fine you don't have issues for that drive cycle, but the odd smelling exhaust sounds like possibly a misfire issue.

Does your car have the Mass Air Flow (MAF) sensor between the air filter and the throttle body? Have you tried tapping on the MAF sensor with the handle of a screwdriver when the engine is idling fine? What happens, if anything? I don't recall if GM was still having issues with MAF sensors in 1990, that's probably something that the regulars on the Bonneville forum would know.

-Rod

[maxwedge]

Maf's had issue then also. So did the egr eqipped cars.

[tannerr52]

It has all new spark plugs and wires...as for MAF sensor i cannot test while running normally because the car doesnt really run normal anymore...

[shorod]

If the car will stay running, even if you need to give it some throttle, you could still tap the MAF and see if the way the engine is running changes, for better or worse.

-Rod

[tannerr52]

Its not maf...When doing your trick, nothing happened...But i believe, after doing some research, that it is camshaft position sensor. THis is something i turned up:

A failed camshaft position sensor will show up in a number of ways. The worst-case scenario is that there is no spark in the combustion chamber. Other symptoms related to the position sensor can include excessively long cranking time when starting cold, rough running on an intermittent basis, poor idle, stumbling or hesitation, a drop in mileage and stalling upon acceleration. These position sensor trouble symptoms may also be caused by a failure in the wiring of the sensor.


Read more: Camshaft Position Sensor Failure Symptoms | eHow.com http://www.ehow.com/about_5903731_ca...#ixzz20oGDiq18

The car is doing all of these symptoms, so i believe that this is the problem...but how to fix it? Yes the car takes a long tme to start, as well as bad idle. At first I didnt think that tis was it because the cam sensor is new...but I don't know...any ideas?

[tannerr52]

Maybe its the Camshaft Interrupter? How much does this cost to replace? it involves taking the timing cover off... :/

[MagicRat]

Regarding the cam sensor error. These 3800 engines were notorious for this. The sensor itself is rarely at fault. Usually its the magnet attached to the cam itself that fails.

The cam sensor is only useful for the ECM to time the sequential fuel injection upon initial start-up. Without it, the ECM goes into a batch-fire mode where two injectors fire at a time. This means a bit of extra fuel piles up on each intake valve when they are closed. My guess is that this affects fuel atomization at low speeds, hence the rough running. But since the rest of the controls function overall the engine does not run richer, and mileage remains unaffected.

I've owned/driven three 3800-equipped cars all with this problem. They all behaved the same way - slightly rougher idle, slightly longer cranking times to start, and, oddly enough, slightly more power at WOT with accompanying better acceleration.

Frankly, fixing the cam sensor magnet is a big job, so I never got around to fixing it. I just let all these cars run with the slightly rougher idle and enjoyed the slight power boost.

[tannerr52]

Yeah, after searching through a ton of forums, I've found out that that is it. Big job for just a 10 dollar part, huh? I've read a few "hacks" on how to do this without taking off the timing cover. As for just letting it be...eh, I don't know...its running pretty rough.

P.s. I tested the connetor at the cam sensor, and it is readng at around 10v with the car off, so I know that it is getting signal...should've tested this long ago but still.

[tannerr52]

Look at me, doin all this researchin! This is a easy method I found...

http://padgett.performanceresearch.us/cars/cammag.htm

Lets be honest...I would love to do this the right way but that would take FOREVER, for what it is worth. This car has over 200k on it, i mean its worth a shot.