Tuned Port Injection Problem

[TPI]

I have a problem with my fuel injection, the ecm goes into limp mode, where would i start. Its dependable, never quits, just dont have the power a small block should, no service engine codes of any kind. Hooked it up to my brothers snapon scan tool, and it says its in limp mode. The only other thing that came to my attention is that it would go to closed loop, detects rich exuast, switch back to open loop, detects lean exaust and so on, it constantly goes back and forth. Any Ideas?

[sorj]

I had same problem but I'll need a little info from you. Headers?, Where do you have o2 sensor? What wiring harness and circuitry did you use? Do u have a performance chip in it? What cam are u using? Be very specific, maybe I can help. Here is what I got: 5.0TPI out of 86 transam with comp cam, speed pro pistons, etc. You name it, I got it but I had some bugs to get out in the process. This being one of them. After I got them out, its been a daily driver for over 2 years. This is what I had to do to get rid of it. Change cam because a TPI engine cannot go over a 112 degree center line (which not too many people know that and sold me the wrong cam because the mellings book said it would work), install a heated o2 sensor (because headers will not allow proper heatup on original design and scavanges too much exhaust which keeps the ecm in lean mode). Changed prom to hypertech power (cool) chip and thermostat to allow engine to run in closed loop at 160. There are custom burn chips you can get but you pay out the butt for them. I used the suncoast converstion wiring diagram off of ebay. You have to ground park nutral wire to alow computer to think it is a standard tranny. Changed the tailshaft housing, vss, and sensor from camaro to s10 (it will work, trust me). This allowed me to maintain antilock brakes, speedo etc. The only two glitches I have now is that when I first start the truck, the check engine light comes on because the o2 needs two minutes to warm up (with chip, it goes staright into slosed loop upon start up). After two minutes are up, shut off engine and let set for ten seconds and restart, light is out for rest of day. Second glitch is the throttle will creep up when first start up is done because of thinking it is a standard tranny. A lot of people forget this engine idles from factory at 1000 rpm (not 750 or 500). So unless you get a custom burned chip, this will continue. Email me your specifics and I'll see if I can help. sorj

[TPI]

Here is what I have. Painless wiring harness for 1987 tuned port injection for an automatic, stock ecm from 1987 iroc z 305 HO, this is a mass airflow system. My truck is a 1992 s10 that had 4.3 and 5 speed(NV3500). I am still using the 5speed with the vss hooked up so my speedo will work, also going through the ecm, I have stage 2 hypertech performance chip and 180 thermostat, stock camaro manifolds for exuast, heated o2 sensor. Now, yes I know that a 305 ecm and 350ecm are different, I have a 350 in it now with the 350 knock senser. I used to have the original 305, TPI ecm, knock senser all in the truck. The only things that werent hooked up were, smog diverter, canister purge, and egr diagnostic temp wire, this is because wiring came without these wires. The 350 setup runs exactly as if I never changed the motor, slugish performance, bad gas mileage, I know i need a custom chip for my setup now but the 305 ran the same way. The 350 is bone stock, cam for computer control. Whatever my problem is was a problem before I put a 350 in it the only thing that wasnt exactly the same in the truck compared to the camaro is a 5speed instead of automatic tranny.

[aceez71]

This may or may not help.I believe the 92's had abs which means it has a drac module. I don't think the ecm will recognize this as a buffered 2 pulse per mile signal. If possible get a scanner from someone and drive it and check what the computer sees as the veh speed. The mass air systems need a 2 pulse per mile signal not a 4 pulse per mile. Also the only experience i have with limp home mode is the chip not being seated correctly and once the ecm got wet and fried the memcal forcing limp mode. I burn my own chips for my truck and my wifes camaro i have accidently cocked the chip on the adaptor and forced limp home mode. Also a bad chip will sometimes act the same. Second note the ecm for the 305 and the 350 are the same the memcal is the only difference

[TPI]

I've tried 3 differnent ecms, all for 305 1987 camaro. I have run the ecms with stock prom and with hypertect chip, they all run the same. When your vehicle went into limp mode did your service engine light come on? Sometimes I think that it might be something simple, it usually is what gets me. That or I need to bang my head into it a few times, one way or a nother somethings going to change, probabaly my face! lol

[aceez71]

I think at least you can check this out and eliminate any possibilities of a bad or incorrect knock sensor. Also did you reconnect the esc connector when you set the timing. That would have thrown a code though. read all of it http://www.thirdgen.org/techboard/tpi/488300-de-sensitising-kncok-sensor.html

[TPI]

thanx for the info on the knock sensor, didn't help though, but it was worth a try. Havent figured it out so I pulled the whole harness out and going to try a refund. Painless has lifetime warrenty against defects, and the only thing I havent replaced is that harness. Have correct volts to everything thats supposed to. No service engine codes either. You know I called their tech line and the guy asked me if any engine codes, I told him no, then he said sorry I can't help you. S&P, (street and performance) told me that they can't help either being that its a Mass air System. This sucks. Carb has power, but I really want that tuned port on there!

[frank53]

Where did you get ECM (not chip)? Reason I ask cause I put a 350 TPI in my 87 4x4 blazer and had service eng. codes problem.I used harness from doner camaro and spliced into blazer harness,to make a long story short I replaced ECM (not chip) with one I bought from TPI specalties in Fla. Everythings ok now.Runs like a scalded dog now and no codes. Good luck.

[TPI]

Im tired of messing with the painless harness. I've been messin with it for 3 years, and havent gotten anywhere with it, hasn't gotten worse either. I pulled the harness out and putting stock original tbi harness in. Going to try Tbi 350, should work with the 4.3 ecm with a 350 5speed chip, correct? Got most of it in, just have to drill out center four bolts on intake to fit old style heads, then we'll see what happens!

[ZR1BLAZER]

if you have a 350 with a 350 ecm and the correct knock sensor i would try the stock chip with a new ECM. when the mother boared goes down its done. if you burn 1 diode it will put you in limp mode.