engine hesitating

matt89imark · Post by **matt89imark** » Sat Nov 22, 2008 9:22 am

Hey guys I hope you can help me out. I have a 87 Isuzu I-mark with the 1.5l turbo. The problem I am having is that it drives fine when cold but when it warms up it has some sriouse hesitation. It runs fine until 3000 RPM's then it dies until the revs bottom out. It will drive normally under load with turbo boost. If it is hesitating badly it will not increase in revs unless I put the clutch in and rev to about 4000 RPM'S and acelerate hard afer that. The second I try to dive a consistant speed it just dies off. Any idea's about what could cause this? Thanks for any help.-Matt

Post by **wedgenut** » Sat Nov 22, 2008 2:29 pm

Hey dude, I could list a million things and none would be right so best you go through all the basic diagnostics first. An intermittent fault like this could be anything but you can check things like, Fuel Pump pressure, change fuel filter if not done recently, make sure AFM isn't sticking if it is the flap style. Another couple of possibilities are the EGR valve or O2 sensor. Then again it could be a coil problem or even a loose ECU plug.
Probably best you take it someone with the diagnostic gizmo and get them to run it up. Do you have ECU trouble codes and can you interpret them ? If not go see a tuning guy.

I don't know much about the I-mark so not much I can tell you specifically.

matt89imark · Post by **matt89imark** » Sun Nov 23, 2008 12:16 pm

Thanks for the tips, I am going thru the list of possibilities slowly. Tomorow I'm changing cap, rotor, fuel filter, air filter and ignition moduel as well as cleaning the throttle body. I was just throwing my problem out there to get some ideas about what it could be. I am leaning towards a fuel problem right now. My little isuzu is just a winter car I never expected to drive as I bought it as a parts car for my other I-mark. But insurence regs have stopped that idea. So after sitting for two years I started driving her. I love Isuzu cars and if I can get this figured out I will probably keep her for a while. Thanks for any input you might have.

Post by **wedgenut** » Sun Nov 23, 2008 1:26 pm

No worries, however I would have thought a hesitation in the winter time where you are is probably not the engine at all, maybe you just forgot to feed your team of dogs. have you tried shouting MUSH you bastard MUSH

Hey you never know, I shout at my car all the time. Buy a Piazza or Impulse or whatever it is you call it in your market and you will learn a whole lot of new profanities to impress your friends with LOL

matt89imark · Post by **matt89imark** » Mon Nov 24, 2008 1:26 pm

I never forget to feed my team of dogs and beleive me there's no sweet talking this little Isuzu, she's an old girl and she's been rode hard and put away wet. You have to talk dirty to her. So I changed the plugs, wires, cap, rotor and fuel filter. I figured I would start with the basic tune up stuff first. It made no differance at all. My air filter should be in on tuesday and I plan to change the O2 senser then as well. I actuelly have the factory shop manuel for it but I havent found it yet. I used to be right into the I-Marks (I think you call them Gemini's over there, or at least they do in Japan) I know my 89 had the same engine as the Impulse does. 1.6L DOHC is a great engine. I remember somthing about flashing codes on these OBD 1 Isuzu's. I think you had to jump the two connectors on the OBD port under the dash and then count the flashes on the insterment cluster. Maybe I'll try to find my manuel and Isuzu notes tonight. Later

Madcat · Post by **Madcat** » Tue Nov 25, 2008 4:53 am

Welcome to the site.

have you checked over on www.isuzone.org ???

If I'm not mistaken there are a couple of guys near you.

Jim

matt89imark · Post by **matt89imark** » Wed Nov 26, 2008 2:22 pm

Well I have an update on my situation. I flashed the codes today and I got a code 22 wich means the throttle position sensor. The manual said to disconect the TPS and jump two wires from there and start the car. If I got code 21 then it's deffinatly the TPS, otherwise it would be the ECU or a wiring snag. Once it was detirmined that it definatly was the TPS it said to adjust it and if that did't work replaced it. So I adjusted it fully one way first and it ran like crap even when cold, then I adjusted it fully the oposite way and the check engine light was off and it ran great! So in the end it was a no cost fix. Thank God I have the factory repair manuel! So I just thought I would share.

Post by **wedgenut** » Wed Nov 26, 2008 5:52 pm

fark me! Piazzas are never that simple. Its only after fixing or replacing fifteen different bits you discover it is the dongledinker that has come detached from the wotchamacallit and every job results in at least three band aids for the torn knuckles and a dental bill for fixing the teeth that have been ground to dust in the process. Piazzas? I luv em.

IZU069 · Post by **IZU069** » Wed Nov 26, 2008 6:51 pm

G'damn those Kanuks are smart! Please send a few down here!
Brilliant diagnosis! (Otherwise those TPS are fairly simple hardware-wise - just a "3 position" 3-wire on-off-on switch' problem is the cable/switch alignment).

A recent local fix I saw was the dude who managed to fix his I-Mark equivalent. The "noise" wasn't his diff torsion rod rubbers ec. It was his ignition timing.

Oh Marvin, you are not alone! (That's a Red Dwarf car-park Reference.)

Post by **wedgenut** » Fri Nov 28, 2008 5:07 pm

Oh Marvin, you are not alone!

I should have known you would be a dwarfie! Takes one to know one I guess. Must dust off my vhs collection again.

IZU069 · Post by **IZU069** » Fri Nov 28, 2008 8:08 pm

Not so much a dwarfie, but I certainly felt a kinship with Marvin.
Einstein wasn't right. DeBono was a dikhed. Hawkings was wrong. And I was one year closer than Buffett (apparently the slump has hit?). LOL!