POS88

S4 with S5 engine. Car was fine when driving home. It was at operating temp when all of a sudden it started reving funny in neutral. RPM's were between 1500-1800. It was like someone was pushing the gas pedal.

It wasn't the typical idle where the needle is trying to find a good place to settle at. It was literally like someone was pushing the acclerator.

In gear it wasn't happy below 1500 RPMs and it wanted to accelerate much quicker.


The previous owner disabled the cold start function and I've never had idle issues other than having it a tad low.
I turned the car off and then on and the RPM's stayed at 2400 for about 10 seconds before going back down to 1500 and it did the whole revving thing.

One last thing is that when I shut the engine off it kind of took longer for it to stop if that makes sense. Instead of immediately shutting down, it may have taken an extra second.
I have extreme back pain at the moment so I'm asking all this with hopes I only have to check a couple things and it won't take long.
Thanks for your help and patience

POS88

So I've tried to figure out the diagram on the fsm but the pics are sketchy and I'm new to the car so I need some help on where to find the air adjust screw. I don't even know if this is the answer but I thought I'd try it since I don't know what else it could be.

Would a loss of compression cause what I'm experiencing? The more I read in to it, the more problems it could be, and it's starting to worry me. This is what I'm working off of...
http://foxed.ca/rx7manual/manuals/1988FSM/01_ENGINE.pdf

Anybody in the bay area have experience with this?

Aaron Cake

iTrader: (1)

You have a large vacuum leak somewhere and the TPS is maladjusted.

Also, depending on how the cold start was "disabled", there may be issues. At the back of the throttle body is a cold start cam which holds the throttle plates open (at 1500 RPM, by the way ) when a thermal pellet is solid. As it melts, the throttles close. It sounds like something in that area is stuck or has been messed with.

Disabling the cold start cam is not a good idea in almost every case, so that might give you a few clues about the competency of the previous owner.

DO NOT MESS WITH THE IDLE ADJUSTMENT.

POS88

The previous owner put 15k miles on this set up with the OMP removed as well as cold start and some other emissions stuff he said that the smog people won't detect. He's a big time rotary mechanic up here in Nor cal, but now I think he's full of it.
Is there anything obvious to see if it is the cold start cam stuck? I don't know how it should look normally so I'm not too confident in diagnosing this.

Thanks for the help. Now I can narrow down my searching.

POS88

Quick update.

I took off the IC and checked all the rubber couplings and elbows for leaks and tears. I wanted to take off the TB but I don't have gaskets for it. I lubricated the TB springs and tried to look for anything out of the ordinary. Disconnected the battery and again tried to find something obviously wrong.

I started her up and it didn't rev as high this time but it also never warmed up because I'm low on gas. It wasn't a crazy idle like someone pushing on the gas. It stayed around 1200-1300 this time. I put it in gear and the RPM's acted like they usually do on a cold start. Once I put it back in neutral it went to 1500 and then stayed around 1200.
I know it's not fixed but it appears to be better.

Any obvious vacuum leaks I can check for? Is the TPS hard to adjust? I've read that they can cost quite a bit, but some posts I've read say it's rarely the TPS that goes bad. Conflicting info.
Thanks for any input.

oyy0

why don't you check to see if you have some kind of air pocket in your coolant?

lpeeff

my whip is doing the same thing

POS88

An air pocket can cause what I'm describing? I haven't come across that one yet but I'll burp the system when the weather gets better. I do get the occasional buzzer when the coolant looks to be topped up. I usually just pump the coolant hose to get the fluid going and the buzzer goes off.

I drove the car lastnight and after it warmed up, it drove a lot better than before. I know it's not fixed but it's driveable. If it were a vacuum leak, wouldn't it still persist?

Aaron Cake

iTrader: (1)

In the FSM you will find a diagram of the rear of the throttle body where the cold start stuff is located. Check to make sure nothing is stuck.

Don't lubricate the throttle body. It is designed to operate dry and dirt will accumulate if it is lubricated.

Adjusting the TPS is fairly easy. There are instructions in the Haynes and FSM. But it can only be done if the system is out of cold start because the cold start cam holds the throttle open slightly.

It really does sound like you have a vacuum leak as well.

zracin

Mine is doing this too. I just replaced my radiator... so i guess the coolant thing might explain it. took to mech. who adjusted my idle though to try and fix it, and now its a tad worse....so now im heading to atlanta rotary to fix it

POS88

I found a procedure in the FSM for throttle sensor. I'm assuming that's the same as the TPS? It described having the car warmed up and then connecting a lamp checker to a 5 or 7 pin connection. Then depending if two lights illuminate or one then you adjust the screw in a correlating manner. Somewhere along there it said it could be done with a volt meter but I didn't find instructions for that. So I guess now I have to build a lamp checker with hopes that I've done it right. I'm sure this is all simple, but I've never had to do this with any cars I've owned so of course the first time I'm going to be hesitant and second guess myself.
Thanks for the help and comments.

Aaron Cake

iTrader: (1)

Hmm, actually, skip the lamp tester.

With the car totally warmed up and the cold start system disengaged, adjust the TPS with an ohmmeter to read 1K across the top-left and bottom terminals (looking at the connector with the single terminal facing down) of the TPS connector.