I bought this car about a month or so ago with hopes I’d be able to just research and fix it on my own. When I got the car it had a solid CEL light that wouldn’t read a code and “bucked” on bogs. On the test drive I did, I did do a hot start compression test and it fired right up and still does today so I don’t believe it’s a compression issue. Here’s a list in order of what I’ve done maintenance wise and fix wise based off of what I’ve read on other forums and websites.

1. Oil change/Filter/Air Filter/Fuel Filter
2. Spark Plugs and Wires
- After all this basic just bought car maintenance the bucking bog was still there but the car sounded like it ran much much healthier.
3. Had my Secondary injectors cleaned and dyno’d
- Both sprayed exact same at all rpms after cleaning.
4. Regrounded my Pressure Sensor.
- This helped the car no longer “buck” at all.
- CEL light is now intermittent. Will be off at startup and turn on while driving. Come off and on a few more times at stops and while driving before completely staying on.
5. Bought a TPS adjustment light and attempted adjustment
- After getting it into adjustment with one light on and one light off I will take the car to warmup and do some pulls to see if the bog is there. I will be able to do about one or two before it starts bogging again. Put the test light back on and it’s out of adjustment. Before I buy a $500 tps is there a way to diagnose it as faulty?
6. Regrounded the ECU
- Ground looked a little green but not too bad, decided to do it anyways. Did not change anything after reground.

Here is where I’m at currently. A few more things I’ve noted is the previous owner put a very poorly done after market exhaust on. I was waiting until I fixed the bog to get to this. He also said when he tried to get the code to read it wouldn’t but then once the OMP did read as a code. I do premix 5.5oz per full gas tank just incase the OMP is our. Any other suggestions on where I should go moving forward?

The car is a 1990 GXL 5-Speed.

Edit: I can take the car past 3800 but only at about 30-40% throttle. I don’t hit a wall. I took the car on the highway and got it to 80 just very slowly. When I throttle it at 3800 it almost sounds like it’s in launch control(2-step) or misfiring.

 

Kind of a bump, just replaced the TPS sensor and still no fix. Even after adjustment of new tps

 

are your AUX ports free and functional?

 

Could you possibly send me a thread on how to test if they are functional or not? This is the first time I’m hearing of checking the aux ports for the 3800 bog. My next idea is the exhaust. I think it’s straight piped and possibly has no back pressure

 

Just go down to the lower intake and look for 2 valve looking things, and try to press the rod in. If it doesn’t move it’s stuck. If the car has no back pressure they won’t operate either, straight piping will do that.