enriquezestevan

Hey guys im new to this formula so ill just give a little history on my current car along with its problems. I have a 1987 944s which runs good, however on certain occasions like in neutral after hitting the throttle my rpm will increase steadily but when it decreases it drops way below 1000 and has sometimes even shut my car off. I can be driving down the street then ill shift into neutral and the rpm will still decrease rapidly. This problem only seems to happen when the engine is cold. After a little drive this problem does not happen any more or if it does its not as severe. Now to mitigate this problem i have replaced numerous things with the last items being my oxygen sensor and a new idle control vavle but nothing has worked so far. I have also checked my tps and others sensors and everything seems to be working fine along with no vaccum leaks. This has lead me to think about my fuel injection temp sender. Now has anyone had problems with this before or does this sound like a good place to look? Any help is much appreciated.

mel_t_vin

Welcome to the forum. When you get the chance, post up a few photos of your car.

As to your idle/stalling issue, I would've suspected the ICV. You mentioned you replaced yours with a "new" one...would that be new-in-the-box or new used?

It certainly couldn't hurt to pressurize your intake tract, downstream of the throttle body, and look/listen for vacuum leaks.

Also, if you search this sub-forum, there are other threads with links to Clark's Garage giving step-by-step instructions for electrically testing the TPS and AFM.

If your ICV is brand new and you don't have any vacuum leaks, I suspect you may have a faulty idle circuit in your TPS.

enriquezestevan

It was a new in the box ICV. I guess I can always test my new one to see if its working properly. I found the process to test the ICV, however, on the test it utilizes one with 3 pins on the bottom and my old and new one only have 2. Awhile back I did test both the AFM and TPS and they both worked properly according to the instructions on Clarks Garage. Ill try testing the TPS again this weekend. So you don’t think it could be something as miniscule as the fuel temp sender? Ive also been doing some reading on the speed and reference sensors since occasionally my car is difficult to start so possibly testing those two things may help as well. Ive tried to spot both sensors from just peering down but this seems easier said then done.

william_b_noble

fuel temp sender?

mel_t_vin

Purchased from a reputable vendor or off of ebay?


No such thing on a 944.

But, as you mentioned this is primarily a cold start issue, you might look into testing your DME temp sensor [blue head, on block, drivers side, near main water neck, adjacent to cylinder #1].


Follow the intake manifold back to the firewall and you should find an aluminum bracket with two rectangular connectors and [maybe] one round connector. Follow the two rectangular connector wires down to the clutch bell housing, sifting through a mess of wires, to two small black connectors, each attached with a single 10mm[?] bolt. Voila...

enriquezestevan

I got it off pelican parts. Really there is no such thing because i have seen alot of people talk about a fuel injection temp sender and i have found the item on some websites and it does have a blue head, maybe i just called it the wrong name. Anyways, yes it seems to occur more often when the engine is not quite warmed up. After a good 5-10 mins of driving it seems to stop or reduce the severity of the decline in rpms. Ill check clarks garage to see how to test it, thanks. Ill have to give it another go searching for those two sensors; looks like i have a few more things to test.

konakat

I've read that rev-down is when the highest vacuum occurs on the vacuum system, so maybe it is something vacuum sensitive?

enriquezestevan

it would be nice if it was something like a vaccum line but there is not evidence which supports that may be the cause, although i will continue to monitor just incase it develops into a vaccum problem. Im still waiting to test out the other possible explanations and when i do i will post what the results were.