Recently picked up an 88 for my son's first car. It has about 125k. I have done a full tune up, plugs, wires, coil, cap and rotor. New GM MAF, SeaFoamed it, cleaned the throttle body and IAC(man they were nasty), and replaced the fuel filter. Bought a new o2 sensor, but have not been able to get the old one out. It starts up, but runs rough till it gets pretty warm, and chugs if you press the gas pretty hard. Once you get to speed it seems to be fine. I had the trans fully rebuilt by a family friend, every part in the trans is new including the converter. Am I looking at an intake leak or the crappy original injectors. South Bay has Bosch II's shipped for $130. Any ideas? Thanks in advance for any solid input. I have already learned a lot from TGO members. This place is awesome!

 

Remove the MAF and take a look at the orange film inside against a light. The film needs to be completely flat for the MAF to send a proper signal. If the film is not flat, get a new one. Also check the relay.

Could be clogged injectors, but this problem is indicative of a bad MAF (been there, dealt with it... car would stall until the temp gauge showed at least 120*F when the original MAF was bad).

If you determine the MAF to be good, use a multimeter on the CTS under the throttle body when the engine is cold and find the resistance. You need to compare the resistance of the sensor to the ambient temperature.

If you're having trouble with removing the O2S, you can either heat the bung around the base of the sensor, cut off the wire and use an impact on it or a big breaker bar with a 7/8" socket, even with a jack if you have to. Get some anti-seize compound and put it on the new one liberally (on the threads only, don't contaminate it).

 

It has a new GM MAF. Picked up a Firebird one off eBay and removed the elbow. A little patients and a hack saw. It does not stall, its just has a rough idle and seems to chug if you hit the gas hard. I was also thinking plugged cat.

 

Plugged cat won't show until the engine warms up as it takes that long for the exhaust to back up into the cylinders.

Definitely check out the CTS... Running too rich will cause this as well, and the CTS is usually the culprit if the MAF has been replaced. Could also be that the ECM needs to be reset with the install of the new MAF.

Check the plugs as well. I'll bet they're black. Is it throwing codes?

 

It does it as soon as you start it. I think i'm gonna get an intake gasket set and fuel injectors from South Bay and see what happens, unless anyone has a better idea.

 

Coolant Temp Sensor... If you can, check it with a meter. If this bugger is telling the ECM that the engine is in the subzero temp range, like it can do when it fails, the ECM dumps TONS of fuel into the cylinders. This causes chugging, practically black smoke out of the exhaust, usually the radiator fan runs all the time, serious lack of power and throttle response. The CTS is cheaper than the intake gasket set (running rich means you DO NOT have an intake air leak), and is 1/10 the cost of the injector set. If you pull a plug and it's black, pull another. If they're both black, we need to find out why the ECM is dumping fuel into the cylinders. This rich condition also causes a noticeably high tone in the exhaust, and you will know the difference when it's corrected.

Check the CTS and then the fuel pressure, if possible (don't know what kind of equipment you have at hand). High fuel pressure can do this as well, but I'd check the CTS first (as it's cheaper to replace the CTS as opposed to having the return side of the fuel system blown out).

 

CTS is near the water neck correct. Don't have a fuel pressure gauge, but I have a degree in electronics and do electronics and PC repair so I can handle pretty much anything there. CTS is pretty cheap. This car sat for about 4 years before we picked it up, so it could be just about anything. I may just pick one up and replace it. I have not noticed any black smoke.

 

I have not checked the voltage on the TPS yet either, so could it be just dumping fuel if that is off?

 

1. The CTS is the thing near the thermostat housing "water neck" and has the ROUND connector. The SQUARE connector is the cold start switch, don't worry about that.
2. If the engine isn't idling around 2-3K, don't worry about the TPS as it's fine.

There are other things to check, but checking the CTS is a good place to start. Just don't break the locking tab off of the connector. If you can't find the temp to resistance chart someone on here posts, let me know as I have the chart in a service manual. I'll need the temp and the resistance of the CTS.

If the CTS tests okay, see if you can borrow a fuel pressure gauge from a friend or someone and we'll go from there.

 

It's been raining almost all weekend so I have not gotten much done on the car. My tiny garage is full of stuff right not. That won't be a problem in a month or so when I build my 26x28 garage. Can't wait.

 

Finally had some free time and nice weather at the same time. Put in a new CTS and ignition module. It is running better, but still really rough when it's cold, and also seems to backfire in the intake if you press the accelerate hard when it's cold. Thinking about timing. Don't have a timing light, but I can borrow one from a friend. Anyone have any thoughts?

 

I have exact same problem, and dealing with a few more, as you can see in my other post.

Anyway, I used to correct this issue by simply putting some fuel injector cleaner and driving on the highway for a full tank. It would take care of this issue for the next 2-3k miles, until the issue would once again start and I would have to do it again.

 

We have been driving the car more and it is getting better, but still not quite there. I am going to borrow a timing light from a friend and check it. I'm looking for a little guidance on setting the timing. I'm an old school carb, no ecm guy. I know from looking around here that I need to disconnect the ECM timing wire on the firewall near the blower motor. I am assuming there is a dist. hold down bolt to loosen. It seems 10 BTDC is where I need to be. Am I missing anything. I'm also thinking about unbolting the cat to see if it helps since I think it's the original one.

 

If you can't easily get a hold of a timing light, and you can get a vacuum gauge, set the timing until the vacuum is at it's highest reading. It won't be 10* BTDC, and will be more like about 16-18*, but it should allow the engine to run pretty well and have a little bit more torque as opposed to the stock timing.

Also, take the cap off of the dizzy and try to turn the rotor by hand. If the rotor has a ton of slop in it, you might want to pick up a timing chain. The dizzy bolt is on the passenger's side, way down under the trans dipstick and the lifting eye. Use a 6-12" extension, u-joint, and a 15mm socket to get at it.

And yes, I know it's expensive, but if your cat is the original, you probably need a new one as the old ones are very restrictive when not clogged with carbon and other garbage.

:edit: BTW, if you haven't figured it out already with all the work you're done to the car, all of the fasteners are metric.

 

The exhaust is going to need to be replaced anyway, so if I need to do the cat do, oh well, I just want it to run good. The computer controlled V6 thing is new to me. I can work on my 455 Trans Am in my sleep. I can get a timing light pretty easy. I am assuming the #1 hole is the front drivers side, and there is a hold down tab on the dist. Can you get to it with a regular wrench, or do I need special one, and I'm guessing it's metric. Thanks for all your guidance Maverick. Me and my son drove his car to the first cruise night here and he had a blast. He is only 14, but had a girl in an IROC check him out. His response..."I feel so cool!" I just want his car to run as good as possible and be reliable.

 

The #1 hole is front PASS side, not driver's side (cylinder closest to the front of the engine is always #1 and pass side is closest, our engines were intentionally made backwards).

It's pretty difficult to get at the dizzy hold-down bolt with even a dizzy wrench due to all of the crud that is in that area on an auto-trans car, which is why most of us use the ratchet, extension, and the flop-joint with the 15mm socket.

 

Yep, I know about the metric. At least they are all metric. I had an 85 olds that was about half metric half SAE. You would have every tool you owned out by the time you were done with a project. I need to get a new u-joint for my socket set since I made the mistake of loaning it to some one.