Car will not stay running issue.

[Boostmaniac]

Hey guys, it's been a bit since I have talked to you, but I have an issue on a car that is starting to boggle me a little bit, here is the info I have so far.

Someone bought an 88 TII (great shape) that will not idle, I decided to drop in and take a look and see what was up, this is what I have gathered so far.

Car will start when cold, go through AWS, then drop back to death with a slight pause around 1k like it is trying to idle.

Car will start when hot, but shut right off afterwards.

Car can be kept running with a light modulation of the throttle.

Car will drive and boost, pulling VERY strong to redline.

No unusual smells, spills or audible leaks.

I have checked the usual suspects with the tools I had at my disposal. I plan on testing the TPS for giggles and perhaps swapping the BAC for one I know is functioning. So my question is, besides for a vacuum leak (which is next on my list of things to do) what the hell else could it be that I am forgetting here? I thought MAF, but the fact that it drives perfectly in vacuum and boost makes me not think that. (I also hear no boost leaks)

Other info.

Looks like the EGR was removed and blocked, going to double check that to make sure it was blocked appropriately, but it looks like a pro job.

Everything else is dead stock.

Ideas?

[Boostmaniac]

Anyone?

Replacing the TPS did nothing. I am running out of options.

[vex]

Honestly sounds like a vac leak. The only other culprit would be an issue with a major sensor (TPS, MAF, MAP, etc).

[WE3RX7]

Run a check on the BAC solenoid. Does the car have A/C... does it seem to try and idle better/worse with the AC on or off?

Check the turbo inlet duct between the MAF and the compressor inlet.

Of course, check for any vac leaks... especially around where the EGR was blocked off.

[Boostmaniac]

TID checked out fine.

No visible / audible vac leaks, but I do think I am gonna pull the UIM and do the rats nest delete just to be on the safe side.

How does one run a check on the BAC solenoid, I have never heard of that before?

A/C test can't really be done. The car will sustain no idle whatsoever. It just revs down and shuts off.

[mazda master tech]

Check compression. Some times if everything checks out OK, it's the one thing that you can rule out. Seen too many 2nd Gens with the same problem and comp. would show up bad apexs.

[TitaniumTT]

Check the coolamnt temp sender ass well. Make sure you check it at the ECU though so you see the closest to what the ECU sees. Also check the TPS at the ecu as well.

[Boostmaniac]

Compression is on my list of things to check, but the car starts cold or hot almost every single time and pulls / boosts perfectly.

Will the coolant temp sensor seriously do that to the idle? I'll check the readings but I am pretty sure it is working within specs.

I am gonna re-look at the TPS and maybe replace it with another one.

Also, how does one check the BAC?

[Ender]

Buy one of these
http://boostpro.net/prodtester.html
There's a good chance you'll find vacuum leaks you'd never have found otherwise.

[Jeff4764]

Ive actually had the same issue for about a 1.5 years except mine will idle until it gets warm and then once it shuts off It has a hard time starting and wont idle at all. I changed so many different parts including the TPS, BAC, MAF, both coil packs and just about every possible temperature sensor I could think of. If you find out what the problem is please post it. I gave up on it for about 6 months and now am thinking about just tryin an O2 sensor just for the hell of it.... Im thinking it might just be giving wrong readings and delivering the wrong fuel to air mixture.

[LunchboxCritter]

I have a suggestion that is far from the normal "it's got to be a vaccum leak". I had a similar issue with my car after doing my swap. I tried testing and adjusting BAC, TPS, MAF, hunted leaks, swapped ecu's, etc. My car would bounce at idle once it was up to operating temp. It would bounce between 500 or 600 rpm to 1200 or 1500 rpm. I adjusted stuff until I had it down to bouncing only a few hundred rpms. The car would idle pretty steady around 1200 rpm with the clutch pushed down, but it would shake like I had a fouled spark plug. It was driving me crazy.

I finally figured out that I had wired the neutral switch to the wrong wires on my harness (jspec TII had different connections then my NA harness). Once I fixed that the car works great. I simply had to adjust the idle screw and tps a few times to get it idling at a steay 800 rpm. I'm guessing that if your neutral switch was to malfunction it would cause similar symptoms as I have described. Testing it is fairly simply, it should show continuity in neutral and none in any gear.

I don't know if this helps at all (might just give you something else to rule out), and don't ask why a manual transmission has a neutral switch and a clutch safety switch (still scratching my head over that).