So I have an 86 xt turbo, and it idles rough, acts like a misfire, and stumbles on acceleration in the low end as the turbo is spooling up, if I floor it, full boost hits, and it pulls good, no stumbles... Boost is stock, replaced fuel filter, fuel pump, plugs.... Timing looked ok, replaced o2 sensor, everything is connected also, if you grab the fuel line from the filter to the fuel rail you can feel a pulsing, but only there... Any ideas? Seems to run better if the o2 is unplugged, but still idles rough.

 

Rick

Have you checked the CTS (Coolant Thermo Sensor)?

I have not, would that cause my problems?

hi, the cts is the main thing that controls the fuel mix, so yes it can definately be your main problem. the wires to the sensor are many times the problem on it however. there is usually corrosion on the connection and sometimes it even extends up the wires inside the insulation several inches. most guys just get a new connector with wire pigtails and splice in away from the sensor. it is the same connector like a fuel injector so they are easy to get from an auto supply store. also you need to check carefully for any air and vacuum leaks anywhere on the intake system and pcv hoses and air intake plumbing.

That could very well be the problem.... it almost seems throttle position related.... could be that the CTS is corroded and the tps is an issue (needs adjusted or replaced?), it kinda surges if I set my foot on the gas, like 1/8th throttle, it kind speeds up and slows down speeds up and slows down, just very lightly.

 

I'll check the CTS, I am sure it is probably a problem, 120k miles, it hasn't been touched I'm sure..

 

 

Thanks

Ok, so I checked the TPS, MAF, and the CTS and the thing on the thermostat housing, most all the connectors were super corroded, I checked the CTS wires, and they were ok, it was just the spade connectors in the plastic connector.

 

Cleaned all connections with contact cleaner and then scraping them, and re spraying them.

 

Started it up, and it seems to idle a bit smoother, but it didn't want to rev to save it's life, sputtered and wouldn't rev past 2500rpm..... let it run, feathered the gas a little, and it seemed to run better after that....

 

Was this the ECU re-learning?? It can't be that smart lol

 

Also, the main issue is still there, any other ideas? Maybe a stuck injector? Can I test that short of pulling the injectors and watching how they fire?

 

Rick

Edited July 24, 201114 yr by TurboXT

fuel pressure tested? Specs are about 36 psi.

 

With my 4GLTA I T pieced a gauge in after fuel filter, taped it on the windscreen with 36 psi on it, took it for a drive, and as soon as boost came on, bogged down, pressure dropped to 10 psi. nw pump fixed it!

 

 

I once fixed a Triumph TR6 2500 pi - they are mechanical imjection - whole car had been rebuilt from ground up, went OK, sat around in a show room for a long time, then never start again. While cranking it over there was a whap,whap, whap like a dog tail wagging against the rear inside guard. It was the fuel pressure return line pulsing. Here in the boot was a T pieced fuel pressure regulator with springs and shims and a dodgy little O ring, found similar in a Holley rebuild kit, screwed it all together - owner claimed it had never gone so well. Nice to know his brother, my old boss, was a Triumph specialist - and I fixed it

Sorry for the thread resurrection... :-)

 

I was wondering if there was any resolution to this? My '87 XT is exhibiting some of the same intermittent hesitation issues.