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Old 07-04-2008, 09:34 AM   #1
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Default strange bipes, ecu, tps, etc problem

I installed a bipes/jrsc on a friends '91 the other day and he is having problems with it. I have not been able to look at the car due to my work schedule but this is the problem as he describes it:

"The idle seems fine to me so I tried to drive it. As soon as you try to step on the gas she would immediately choke out, not stall but you could not get it over 2000 rpm's. Put it in neutral and try to hold the rpm's at 2000 she drops to almost 0 then up to 2000 rpm's but not over 2000. The engine is pulsating."

It sounds like something is putting the car in "limp mode". The car ran very strong after the install. He drove it home and didn't touch it for 6 days. The bipes wiring harness wires were pretty brittle at the green connector (bipes side). The CAS IN/OUT wires were installed with quick disconnect bullet connectors and the other wires (+12V, GND, air temp/flow) were spliced in with butt connectors at the ECU (1 wire in and 2 wires out) My guess would be that either the air temp or air flow wires are not making contact with the ECU but I don't know what affect this would have. The CAS IN/OUT wires have been jumped over so the bipes is not sitting between these. The only other thing (other than vacuum tubing and the SC) we messed while installing the JRSC was the TPS harness (it now has one of the JR harness extentions in it) and the ISC harness. Anyone have an idea of where I can tell him to look? It will be three days before I can put my hands on the car for troubleshooting.
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Old 07-04-2008, 12:16 PM   #2
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Originally Posted by rmcelwee View Post
Anyone have an idea of where I can tell him to look?
As much as I hate to sound like a jerk, he needs to look at one thing at a time.

Check to see if the IDL terminal of the TPS harness is shorted to ground (With the TPS itself disconnected).

You already covered CAS.

I can tell you from experience that the engine will run just fine without CLT or IAT. It'll throw a code, but it'll run.

As to VAF, sounds like your most likely candidate so far.

'Couse, if it ain't any of that, then it's something else.

Any stored codes?
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Old 07-04-2008, 04:37 PM   #3
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As much as I hate to sound like a jerk, he needs to look at one thing at a time.
Jerk!

He doesn't really have the knowledge to check any of this stuff and I can't help him over the phone. Actually, I will probably use any suggestions that I get here when I go see him in a few days. No idea of the codes but again it isn't something I can have him check. I'll definitely take a look at the AF and see what it looks like. On another note, both my multimeters decided that this week would be a great time to die! Ugh...
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Old 07-04-2008, 06:08 PM   #4
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FWIW, I asked this question on the power list and Bill Cardell said that decel fuel cutoff was killing me (i.e. it must be a TPS problem). When we installed the SC I grabbed an old TPS cable extension (male/female) and threw it on his car. I have no idea where it came from and don't think I have ever used it before. I'm now assuming that is where the problem lies. I just hope the owner can troubleshoot it from this point. I hate to make him wait 3 days before I can get over there to help.
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Old 07-04-2008, 07:25 PM   #5
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Yeah, I agree with him. Like I said- investigate whether the IDL wire of the TPS harness is shorted to ground. On a '90-'93, it's the red wire which winds up at 1N of the ECU harness. If that wire is grounded, the ECU will interpret it as throttle closed.

Or, if he can just pull the thing off entirely, the engine will start and run just fine with no TPS connected at all.
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Old 07-08-2008, 10:48 PM   #6
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The problem was....


The TPS cable had some sort of oily liquid in the connector. Very strange! In addition, the CAS connector had scaled corrosion in it. Probably contributed to the horrible running condition. Everything was running fine when it left my house. Only when the owner got it home did it decide to crap out. Thanks for the help guys!
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Old 07-10-2008, 10:23 AM   #7
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OK, the car is dead again. The guy drove it to my house the day before yesterday and we worked on the idle and fuel pressure. Everything was great and he drove it home. His wife took it to work yesterday and when she left to go home for lunch the car was doing this:

When cold - The car will start but the idle hunts.
When hot - The car will stall unless you keep your foot feathered on the gas.
When warm (let it cool down after it stalls) - The car starts, the rpms go to 1000 and then it dies.

I still have not seen the car when it is having problems (runs GREAT when it is over here). The car was towed to my house last night so I can take a look at it. Any suggestions?

FYI, I will be looking at the CAS connector and the TPS connector first as well as checking/clearing the codes. I won't have much time to mess with it today but hopefully I can find something.
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