madmax204

I have an 88 turbo, car has a Rtek 1.7 ecu, RC engineering 750cc primaries and secondaries, 3" inch, large front mount, aftermarket fuel pressure regulator.

So here is the issue I am having.

When I start the car cold, it goes to its normal 2k idle then it drops off and dies. It does this repeatedly until I have done it enough times that it has warmed up and it stays idling.

Once it stays idling, it REALLY stumbles revving it. Like it acts like I have a vacuum leak. I have verified with near 100% certainty that it is not in fact a vacuum leak. I have welded together a piece of pipe to make a loop from turbo to throttle body so there is very limited connection places.

I am kinda lost as to what else I can look at, I have adjusted the TPS so that only one light comes on, I have like I said pretty much verified there is no vacuum leaks, I think the fuel pressure might still be high (around 35 psi at idle) but the stuttering I can't figure out.

Any suggestions? What can I try? What other info do you guys need to maybe provide a little more of a educated guess? Anything I can try is hugely appreciated.

madmax204

Anybody? Im off today and would love to know if there is anything I can try!

satch

iTrader: (1)

The primary injectors could be clogged. You could have a poor engine ground. The AFM could be problematic. Engine could have low compression. Spark plugs might be insufficient. Water thermosensor might be problematic.

madmax204

primaries I have recently flow tested and they should be ok. Engine ground can I just add a big ground to it and to the body? How can I fix a problematic AFM? Spray it all clean with some contact/electronic cleaner? I know the compression is good, just checked and its a recent rebuild with 3mm seals. I will check the plugs! Will also check the thermosensor.

satch

iTrader: (1)

There's a procedure in the FSM to test the AFM. You could also bypass it for diagnostic purposes by unplugging the unit, which is required to test it, and w/it unplugged jumper the fuel check connector and start the car and see if it runs better. W/the AFM unplugged the car wil run very rich which will cause the exaust manifold to get very hot and glow so you don't want to run the car for long in this manner. The way the car runs will give you a heads up possibly.

The thermosensor should read 2 to 3 volts -cold engine w/key to on and .5 volts fully warmed. ECU pin is 2I and the wire color is White/Green.

Either redo the existing engine ground if need be or splice new grounds into the existing ECU ground wires (there should be 4 of them) and ground the new wire to the ECU mounting bolts.

madmax204

Is it possible the rc750s are too big? I feel like its just gettin way too much fuel at idle-3k rpms, over that it revs like a champ and sounds insane, but at idle no matter what I do its just eyeburningly rich

BurntOrangeT2

iTrader: (30)

The 1.7 Rtek cannot compensate a net of 400cc more fuel on just the primaries.....no wonder this thing won't idle. Also considering you have an aftermarket FPR (which u don't need) that's not helping either. You need to find out the stock operating FPR psi at idle. If u have some stock primary injectors put that back in along with some S5 T2 fuel rails and go from there. Shouldn't cost more than $100-$125. Also, either sell the 1.7 and get a power fc or get it upgraded to a 2.1. The fact that you have a front mount, a full 3", upgraded injectors and no way to tune this thing is not a good stage to be at.

One other thing u can do if you have someone to help people is turn the fuel pressure down while a buddy is keeping it at 2-3k rpm and see if it will idle better, hopefully ur FPR has a gauge on it.

KompressorLOgic

iTrader: (6)

ya that's way too much fuel at low rpm/idle, why don't u at least get the 1.8? burnt orange is right tho the 2.1 would be a better way to go tho

madmax204

Sorry let me clarify, I mistakingly said it was a 1.7 its actually a 1.8, I also have all the emissions systems removed, BAC removed.

The FPR is a cheap-o one, and I can't seem to get it to go below 2.5 bar at idle. I will see if I can get my hands on some stock injectors (at least for the primaries) and a stock ECU just to check and see if that makes a difference.

I fiddled with it today, to my knowledge the AFM is working properly, checked the plugs, it just seems like its getting way too much fuel, and when coldstarting, it goes to 2k rpms then dies, does that several times then I have to coerce it with pedal feathering to reach idle without dying.

BurntOrangeT2

iTrader: (30)

Your best bet is to either get stock primaries in, getting the fuel pressure down, or go to a 2.1 which will allow further expansion of your fuel system, much better tuning and driveability performance and all around easier to get your car running.

madmax204

I will have a look and see if I can get a hold of some stock primaries, and get the factory fuel pressure regulator back in.

madmax204

This might seem like a silly question, but if I put stock primaries in (550cc) will the RTEK recognize the fact that they are no longer 750cc? Or will I run super lean?

clean87

iTrader: (1)

ecu always needs to be reprogrammed for the injectors that you are running

BurntOrangeT2

iTrader: (30)

The problem is the Rtek doesn't know what you have in terms of injectors. You only have the ability to tell the ecu what capacity your injectors are in the 2.1 version. Which is what you need.

Read: Rtek7 ECU Upgrade Technical Information

madmax204

Hey guys so update,

I checked the injectors, they are good. I checked and re-did all the grounds, all good. New plugs, re-dialed in the TPS, nothing seemed to do anything.

I put in a stock N333 ecu, car fired right up and ran/idled better than I have ever heard. Free revs perfectly without hesitation, so I took it out for a spin. It ran fine until I gave it a hard boot, then it started stumbling and farting again and was hard to keep running. I got it back home, and it idles but its a little goofy. Is it just too much fuel? I left the 750ccs in there for now. Or did I pop a vacuum leak? I tried checkin it with an unlit propane torch and didn't see anything at all, was quite thorough.

satch

iTrader: (1)

A stock ECU and aftermarket FPR might not be a good match.

barkz

iTrader: (1)

I'm leaning towards a bad chip/poorly installed chip. I had a very similar issue with my 1.8 I installed myself thinking my solder skills were up to par. I burnt out a connection and had issues. Plugged in a stock ecu and worked fine. I now have the 2.1 and am just waiting to tune it. Unless you want to buy it to fund my PFC purchase 😉

madmax204

well the ECU still has all the stickers on it from when it went to Rtek, so I don't think it was a home-done job, I bought this car as a basket case that I'm 100% certain the previous owner had zero idea what he was doing, so its been a matter of trying to fix his mistakes the entire way here.

Satch I am thinkin same thing, but am struggling to get my hands on a stock FPR

satch

iTrader: (1)

An aftermarket unit can do the proper job but it depends on the range of its ability to create the proper psi as some are not capable of lowering it to the proper level.