Yesterday I was reading through Chuck Westbrook's notes on adjusting the throttle body and TPS. I've always had a semi fluctuating idle and finally decided on taking action. I removed the throttle body to have a better look at the TPS. I decided to go ahead and remove it almost completely by removing the two screws and the nut inside the sensor. I adjusted everything behind the TPS according to the specs outlined in the notes. I then replaced the TPS and throttle body back on the car and put together everything. I went back in the car and saw 0 voltage VTA1 and VTA2 on my PFC. After some thinking, I decided to remove the TPS and inspect it. I realized I had installed it incorrectly (the sensor wasn't catching onto the copper looking hooks). So I finally replaced it correctly and adjusted the TPS to the factory limits on VTA1 and 2 open and closed. So I finally put together everything once again. I tried to start the car and it wouldn't start. After cranking it a few more times and giving it some gas it finally started. It sounded horrible! The idle (with out supplementing gas) was at 400ish rpm and the engine was shaking pretty bad. I immediately shut it back off. I decided to recheck my work to make sure everything had been replaced properly and TPS voltage within spec once again (I found nothing), I then tried to start it once again only to find the same problem.

Any ideas? I'd appreciate any help I've done a ton of research in the archives and in any problem many have had before with no solution. Thanks!

 

It hurts my head to even post this.... but check to make sure your MAP sensor pressure line didn't come off. The sensor is on the firewall behind and above the throttle body.

 

Yes i Also thought that may have come off. I checked it and it's connected to the back of the uim. I also checked and made sure it's connected. MAP sensor is fine. Thanks though. Any other suggestions?

 

Sounds like a horrible vacuum leak. Maybe you disconnected something accidentally.

 

Which hose could it be though? I only disconnected the elbow, throttle body, and the tps sensor. I've looked through everything several times, removed And reinsed everything several times. I can't see anything that I could have done wrong. Would an improper adjustment to the fast idle cam and associated screws created this problem?

When I put everything back together the first time (when vta1 and 1 read zero) I turned on the car and it sounded and started fine, the idle was in the 700s range. The tps values were just off though (since I had installed it wrong)

 

How many turns from full closed is the air bleed screw (under the TB)?

Did you turn the idle adjusting screw clockwise to raise the idle (8mm jam nut and screwdriver)?

 

Was it staying at a stay idle or was it idle searching that will help narrow down this problem.

 

The air bleed screw is one half turn and the idle adjust screw was turned up until ot doesn't hold the butterflies open anymore. I then tightened the nut.

After everything was put back together the idle is now fixed at around 400rpm but if I don't hold the accelerator, it will turn off. Also if I give it a bit more gas to try and raise the rpm, the engine begins to shake a lot more. It sounds very unhealthy.

 

By idle being fixed I mean stable at 400rpm.

 

I had a similar problem and it happened to be massive vacuum leaks and also a split hose going to the Map sensor that was hard to see. I got it fixed by doing a hose job

 

I don't really have very many vacuum hoses. I have removed all emissions and installed all block off plates for a single turbo. All nipples have been capped off with high temp caps, they're all still on.

The only check valve I can thunk of right now is the one from the map sensor. I don't know how that could have gone bad over a few minutes of adjusting my throttle body.

Is it possible that it may be a grounding issue? I remember having a ground wire that was previously installed on the left upper bolt on the elbow to throttle body junction, I decided to movE it to the right upper nut. Possible? I'll change it just in case. I know that's not the only ground supplied to the engine. There is another one by the firewall.

 

After doing more research in the FSM I found that it may be the fast idle cam. I do remember changing the position of the cam. I adjusted it to what seemed (to me) the correct position according to the FSM. The directions are a bit unclear though, so I may have adjusted it wrong. I will search through the archives to find a more laymans version for the adjustment.

 

The ground wiring is fine. I just rechecked my fast idle cam and other relevant adjustable things on the throttle body and they all seem to be within spec.

Any other suggestions?

 

Sounds like you did it wrong. Might want to get back in there and go through the steps again.

 

I wish I knew what I did wrong. Which incorrect steps would most likely cause the symptoms.

 

Any other ideas?

 

It is probably a combination of items that might be off. I suggest going through the whole process that Chuck laid out. I used his notes when I did mine and it turned out perfect.