I’m starting to get frustrated after finally getting my car back together after installing a new big mouth intake, AS&M runners, and ported plenum. The car starts and wants to immediately die if gas is not given right away and if it dies will only start with hitting gas pedal. Also idle surges after letting off gas when idling, like hitting 450 and going back 850-900. My buddy and I almost think it’s off a tooth but we double checked it and timed it to 8 degrees BTDC. I am thinking the idle air needs to be adjusted to accommodate the aftermarket parts. I also looked at the L98 start up sequence and according to that it’s either vacuum leak, intake leak or idle air mixture on TB. The idle has never been touched either as evidenced by the factory plug in the TB.

After driving 30 miles the idle has improved with the re-learn but still does not want to start up correctly. The FPR is 2 years old as well as the Bosch 3 injectors and no check engine light. I also double checked TPS voltage and did the IAC reset. Fuel pressure is at spec around 43-44 with fpr line disconnected.


When it was idling with aldl droid

 

Get or make a cheap smoke machine and check for vacuum leaks. Especially since it says lean.
I find that brake cleaner checks aren't reliable at all and when you can build a cheap one for probably less that $30 it's hard to beat. Last I looked, you could get a built one that uses smoke oil on Amazon for $80 which still isn't bad.

 

Thats an idea, this was my first try with aldldroid but couldn’t get BLM to read. I’m going to double check timing tomorrow. What’s odd is once it gets nice and warm the idle is better but still doesn’t want to start and stay running unless I catch it and give it gas (acts like it’s flooded almost). It had a massive vacuum leak before that I fixed and it’s idle was very high, over 1100rpm or more, but after fixing that I had this issue.

 

Also the car can be driven around, even starting and stopping frequently, without stalling to the point I thought it was good and then stopped and restarted it but didn’t want to stay running and had to hit the gas while turning the key to get it to start up.

 

I wound up changing the idle air mixture a touch following the instructions in the how to section and now the car starts and doesn’t die and no idle issue at all. I’m sure it’s just masking what the real issue is but at least now I can drive it without having to constantly re start etc. I’m pretty sure there are small vacuum leaks around the runner to base and runner to plenum.

 

Took another crack at it and found a vacuum leak around the driver side front runner to base gasket with my TB cleaner, I loosened everything up on that side and re-torqued it all. Hopefully that will help the leak, they are new gaskets so I might have just needed to reseat it in the right place.

 

As&m quality isn’t what it use to be. If these are new runners you might have to resurface the runner or reinstall
with rtv on the gaskets.

 

Still getting wonky numbers on aldldroid but I busted out my vacuum gauge and I’m pulling nearly 20 inches of vacuum...18 at idle to be exact at the FPR port.

 

I will keep that in mind, good to know that RTV will work. It’s odd how the vacuum is in spec.

 

Maybe TPI just sucks a lot

Glad to hear you're getting it figured out though, I'm putting my rails and runners back on soon.

 

Lol it really does sometimes, but when it runs right it’s pretty good. At least the car can be ran right now but I’m running out of ideas.

 

Tried a cold start this morning before work just to see how it behaves and it started but immediately started hunting for idle from around 500-800 rpms...so back at square one. I didn't have the time to let it get warm and see if it smoothed out but considering how well it ran when warm the temperature seems to play a key part in this. I might order up a set of Mr Gasket 146 gaskets and replace that one runner to base gasket just to eliminate it as a possible cause, at least its on the driver side.

 

May be a cold vacuum leak, that seals itself up as the engine warms, and expands.

 

I’m pretty sure your right, I’m going to order new gaskets and give it a shot. These cars are very touchy with vacuum issues.

 

If you smoke test it, you'll see where the leaks are. It might not necessarily be the tpi gaskets. If those gaskets are still in one piece then use some rtv. The Right Stuff is excellent for the MrGasket material. This is coming from first hand experience with a ported set that I had to modify each set of gaskets for the porting.

 

When I tested it with TB cleaner only one place lit up, driver side front runner to base. I have some leftover Right Stuff from the intake.and black RTV. Would you coat both sides of the gasket or just the side that makes contact with the runner?

 

I stand by using brake cleaner or tb cleaner to find leaks is luck at best. I've sprayed areas that have smoke coming out of them and didn't have anything change in engine rpm. But it's neither here nor there.
I'd coat each side as thinly as possible. You don't want it squeezing gasket out of shape (that's a huge drawback to using rtv in gaskets) but you want to take up the imperfections in the surfaces. As said previously, aftermarket aluminum doesn't always meet the QC requirements of OE

 

Got the gasket resealed last night and tried it today, vacuum leak appears to be gone. Still starts and wants to die immediately and not idle unless the idle screw is pushed out some. I do have some new live data once I got it to idle. It holds nearly 18 inch of vacuum at idle. Smells super rich

 

Do you have a good driver and pass side picture of the engine ? Have a few questions that are answered easier with pictures.

Also, I've noticed several after market lower runner flanges are larger than the machined area on the intakes and have to be ground on to fit.

 

 

Hard to see in the picture but does your driverside have the small tube between runners? (like the small tube on the pass side)

 

Sorry the picture was lousy, it does and it’s blocked off by AS&M because I went with 89’ up runners because I had previously disabled the cold start injector in both the prom and on the rail.

 

IAC count seems really high considering you're in closed loop.

 

was the small hole blocked in the plenum drivers side or does the tuner cover the hole ?

 

I think I know what is wrong, the plenum I have is from an 85’, my throttle body is the original 88’ and with the 89’ up runners something is not playing together. Am I right to assume I need an 89 up throttle body???

 

Or can I pull that driver side runner and unclog that small tube??

 

Might check to see if it’s covered up. A expansion plug and rtv to block or tap to npt and make a plug flush.

 

This is what it looked like when I got it before I cleaned it up and ported.

I received a PM about possibly drilling a hole in my 88’ throttle body to correct this issue as well??



Driver side

 

Might check that area for vacuum leaks. The passage goes into the plenum.
dont see how modification of the tb will block it if it’s a leak.

 

Will do, what I was talking about with the TB was with the 89’ and up runners having that tube on the driver side blocked off on both ends would that effect my 85-88 plenum and throttle body? I was told when I ordered them they would work, I clearly explained my set up too to AS&M.

 

That tube sends the idle air to the lower intake, if it's blocked off by the later 89-92 runners or back of T-body with different parts, it will start and die. You can do some cutting on the triangle area ( front of the plenum) to just let the idle air in the plenum and it would be just fine.
Or port the correct plenum and it would be ok too

 

Thanks! I will do that, any recommendation for how big of a hole etc.?

 

This isn't mine but it's how I do them. For the most part it's mix and match at will then.

 

Right there where I highlighted?


Any idea on how big a hole to drill? I see you that one is gone completely

 

Looks like you have a 85-88 t-body too, If you had a 89-92, you may have gotten away with it working.
3/8s to 1/2 ? Just make sure to clean the metal out really well.

 

The plenum and TB is 85-88, the guy at AS&M claimed this would work and I told him what my exact set up was with cold start delete etc...luckily this is an easy fix.

 

On a 89,90-92 plenum a 3/8 hole is enough for iac passage

 

Thanks! Hopefully tomorrow I can get this done.

 

I wound up going with the TB version of a fix by cutting out a groove in both sides of TB bores to IAC triangle, it worked great! Car idles right up and no more start and die. Thanks again for everyone who helped.

 

Glad I found this. I believe I will encounter the same issue as I am changing my runners over to AS&M. I think I have the 89 up runners since I was planning a 9th injector delete... running EBL so no need any longer. Great info on this board and a few solutions presented. It is awesome when the OP comes back and posts the resolution instead of the thread just ending.

 

I realize that you think it's fixed but your data indicates the MAF at idle is much too high and that's also reflected in the INT and BLM being buried in the negative fuel trim - it's pulling out as much fuel as it can because your MAF is reading almost 10 grams per second when it should be closer to 5-6 grams per second. MAF or wiring is boned.

GD

 

True, after seeing how rich it was the next day or so I put the Bosch MAF back and maf readings went back to 5 and BLM was almost right on 128 same as INT.

 

Ok excellent.

GD

 

Any chance you took pictures of the finished product? I would be curious to see where you made the grooves in the throttle body.

 

Unfortunately I did not but it looked similar to this and is what I used for guidance. You could also reference an 89’ and up throttle body. I made 2 grooves, one in each throttle bore connecting the IAC triangle shaped passage. I used a carbide cutting tool to do the job and it cut easily.





Here is a good thread that explains it as well.

https://www.thirdgen.org/forums/tpi/...8-vs-89-a.html

 

Im having the same issue as well. Except I've got a Stealth Ram. When I start the car cold it doesn't want to idle. I need to help it out, then the IAC kicks in and starts hunting for idle. Usually ranging from 1500 down to 600. But ONLY when cold. If i start it warm. It fires right up and idles perfectly fine. Funny thing is, this only started After I took off the Granatelli Motorsports MAF and put a stock MAF on the car.

 

Thats wild, did you go aftermarket for MAF? These cars seem not to like aftermarket but yours seemed to like the granatelli.

 

It had the aftermarket one on there and idled fine but didnt like to rev over 3K. Put a factory bosch one back on. Now it won't idle cold but it revs to 5K

 

Do you have any way to get a data scan of what’s going on? That might help determine what’s going on or if one of the MAFs is getting messed up readings. I wish I could help more with that intake but have no experience with those.