I like my truck... and a startup question

[scotts90ranger]

I went snow wheeling with my truck today, just got back. My engine ran like a sewing machine with a turbo! For the first time in a VERY LONG time my truck ran without a hickup, purred like a kitten... Minor knock at 10psi with regular fuel, maybe two pings then stops. Idle was relatively steady at 15-17"HG (tach doesn't work right now).

On to the question, the running issue I've been having with the thing for the last year seemed to be a hot restart issue until recently but I believe it's just a startup issue as it happened when I first started it today, ran like crap to the point that it would die within ~5 seconds and would continue doing that if I let it stall and restart it, If you babied the throttle it would keep running and you "could" drive it but is a dog unless you are at WOT, where it still doesn't have full power. Here's the kicker, if instead of letting it stall, you turn it off then restart it it will run great. I do a WHOLE LOT of engine service at work, and design some parts of fuel systems at times and this is completely stumping me... For those that don't know the specs on my engine, it's a '86 Tbird engine with a PC1 ECM running DIS from the original engine with only the passenger side coil pack.

Also, if anyone knows why the tach on my truck doesn't work when I'm using only the passenger coil pack instead of both, any help getting that issue fixed would be appreciated also

 

[Hagan]

What kind of tach are you using? I'm assuming you have an aftermarket one?

 

[scotts90ranger]

should have mentioned that... I'm referring to the stock tach that worked before the turbo swap, I've heard the tach is driven off the drivers side coil pack and if this is the case is the reason the tach doesn't work, just trying to conform this. I believe I have a plan to put that coil on and just ground the outputs, some day...

 

[Hagan]

I'm not sure because I thought the stock tach worked off a coil for a distributor and not a DIS coil system.

Any ideas on the hot start issue?

 

[scotts90ranger]

I believe the stock tach on mine is driven by the ignition module, but I haven't been able to follow it, or haven't looked in a while, maybe I'll look through the wiring again...

on the starting issue the only thing I can come up with is a ground issue, the last starter that went out took some grounds with it...

 

[Hagan]

I believe the stock tach on mine is driven by the ignition module, but I haven't been able to follow it, or haven't looked in a while, maybe I'll look through the wiring again...

on the starting issue the only thing I can come up with is a ground issue, the last starter that went out took some grounds with it...

How long did that starter last for? Maybe it is a ground?

 

[scotts90ranger]

I believe I figured out the problem... I've been out wheeling since wednesday, just got back. While I was gone I got to thinking about the ONLY thing that happens on key on that doesn't change unless you key off and restart, and that is check the barometric pressure! So, I believe I'm onto something and will start looking into that, I sprayed out the reference hole with some brake clean (only thing I had with me out on the sand) and it seemed to help, so I'll swap on my spare after I get that cleaned up a bit...

For whatever reason my idle is screwy right now though, it's liking to stay at 14"HG and sounds like it's about 700rpm, went to screw the idle screw in a bit more and realized it was pretty much maxed out... any ideas on that? Sounds like a bit of a misfire too then, clears up if you bring the idle up with the pedal though, I got a spare set of spark plugs which I'll put in soon... It sounds rich, since the baro sensor could screw with that I'll try messing with that first, if it for whatever reason thinks the baro is higher than normal it would be adding fuel, my other thought is oxygen sensor, which would also explain my lower than normal gas mileage, the heater box has been melting on the O2 sensor for a couple years now...

 

[dangerranger83]

The 2.3 N/A that my truck had (87 FI was in it) would have the same start up problem. It wouldnt run right or it would want to stall until you turned it off then right back on then it ran like a charm. Also its idle would surge then drop nonstop once warmed up. I dont know how this can help but will say that it happened to a N/A 2.3 engine.

 

[Insanejughead]

I read all of this and I didn't see anything about you giving the TPS and IAC a good check.

I've had Idle Air Control valves stick on me to where the engine would run fine one minute (hot or cold) and then stall quickly at other times.

Also, if your idle screw is maxed out and it's dogging down to ~15"Hg, then have you checked your Throttle Position Sensor's readings? Just the other day, my pickup ran fine at idle, but would do the opposite when revved. I thought this was happening because of dirty fuel or clogged injectors. However, after checking the voltage output of the TPS through its swing, I learned that it needed adjusting. It was reading around .95-1.0v at idle when it should've been reading .65-.7v at idle (with engine off, of course). I don't know if your TPS is adjustable, but I would recommend getting one that is.


I'm not calling you out on any of this, but I just wanted to make sure this stuff had been covered through all of your engine checks.

 

[scotts90ranger]

my TPS is kinda screwy, I checked it once but I'm not a fan of the '86 TPS having a sensor with wires sticking out of a very bad area... Part of my plan is to get a '89 or so throttle body and swap on it so I can connect the stock plug that's still floating around in the engine compartment... This has been on the back of my mind, and the throttle will most likely be changed when I rebuild the engine in about a month. I've looked into the IAC a couple years ago and have a couple spares somewhere, again, will look into that when I have the engine out.