Hi, Strange prob. my 88 iroc 350 TPI w/auto seems to be losing power on the top end. Used to bark the tires now it just runs out of steam. the tach starts bouncing around as well but only at high RPMs Any ideas?

 

I'm thinking the coil is the primary suspect, ignition module as the next one.

I've got a spare AC Delco coil on the bench you're welcome to if you want it. Not much help on the ig module.

 

The coil was my first guess and I picked one up at Advanced A-P for $19 and changed it out. Still no good. I remembered an old thread about the erratic tach readings being a sympton of a bad ignition module. Usually, in my experience they either work or they don't. The car is hard to start and usually needs a little throttle to get going. I did have a few codes come up and I changed out the O-2 sensor and haven't had a light since. I probably have at least one bad injector. When I shut it down the fuel pressure bleeds down to 0 almost immediatly. The new motor is almost done, They (the machine shop) is having a problem balancing the rotating assembly. I would really like to fix this before I do the swap so I don't inherit the problem with the install of the new engine. Any ideas? I have a spare ignition module but it is an aftermarket piece and they are NEVER as good as the GM stuff.-Mike

 

Ignition module and faulty grounds like the grounds at engine block having poor contact or a dirty distributer base would be most likely things next. After that maybe its the P/U coil going out.

 

Advance Auto's website shows they can order Delco ign modules...price is competitive w/ what I paid the local Chevy dealer years ago.

 

Well, I guess I'll go get one. Suppose I should get a pick-up coil as well. It could just be that my car is getting old.

 

Check your plug wires... One of mine popped off, and the tach started bouncing around and the engine had no power.

 

Ya know...I'm familiar w/ Mike's skill level so I had automatically ruled out simple causes like this...but it's worth checking for loose or damaged plug wires.

 

As soon as I realized power was down I took it down to my buddy's shop. Put in a new fuel filter. Checked the pressure. Did cap and rotor, plugs and wires and a new coil. I am going to whip up a new distributor to swap in. Could it be the injectors?

 

The erratic tach points to an ignition problem, though. Try to get the ignition squared away before looking elsewhere. Have you checked your grounds? Is the dist. base, clamp, and the area on the intake that the clamp contacts nice and clean? My base had 15 some odd years of grime on it and eventually the car just wouldnt do anything but crank untill I cleaned it and resored a good ground path for the module.

 

what about the air filter, and sea foaming the intake? that really doesn't have anything to do with the tach though. mine was a burnt plug wire.

 

Oh, I have K&Ns and I cleaned them as well. What do you mean about sea-foaming?

P.S. after I did this it ran better but the problem is still there. It still needs a little foot play on the throttle to start as well.

 

eratic tach and slow acceleration? mine has that problem too ('90 Iroc 305tpi).

my tach jumps around whenever it feels like (idling, while driving, just whenever). it's been doing that ever since i replaced the EGR valve and solenoid. i checked the hot spots as in plugs and wires and fuel pressure(everything seems tip top) and still no go on the acceleration issue. sometimes the engine won't start too(but i think that's my starter going bad).

 

I'd check the tach wire going to the distributor first. If that isn't corroded or loose, then start looking for a vacuum problem or leaking E.G.R. valve.

 

Talk about dumb.......
So I look in the back of the car, I figure I'll find my jumper wire and check the distributor ground. I find the old coil, BUT it is not the old coil. Last week when I pulled the coil off the motor I didn't get a chance to grind off the rivets. Something happened and I needed the car. I put the old coil back on and forgot about it. Last night on lunch I swapped the coil and cleaned up the dist. hold-down-Car runs great! Still not as good as it was but what an improvement! Still doesn't start well but the tach doen't jump all over. Thanks guys-Mike

 

good to hear you took care of some of your problems hope you get it running the way it should soon.