Please help

[dohc v6]

Well my car has been getting worse and worse. when i step on the gas either hard or soft i get no power. like it starts to stumble at 2000 rpm. now i checked the front spark plus and everything looks good. also i get a pretty good vacuum reading. but no power. even at 50 in 4 gear it i step on the gas and no power. please help

 

the car is a 94 z34.

[Slade901]

Could it be a blocked or clogged catalytic converter?

[GP1138]

I'm guessing ICM/coilpacks. You've probably got a fried coilpack or two. Also, how is the fuel pump working?

[dohc v6]

i can check the f/p tonight but how do i check the coils and icm

[19Cutlass94]

I just checked the coils by running the car, and taking the wires off one by one and when its good, youll see a nice spark. If its bad, youll know it.

[dohc v6]

thats kind of dangerous seeing how there is like 40,000 volts of power there.

[GP1138]

thats kind of dangerous seeing how there is like 40,000 volts of power there.

 

I've done that before. It's really not possible to TEST them accurately. I've always used my $35 method. I go to the junkyard and spend $35 on a complete known-good set ICM and coilpacks and if that fixes the problem, great.

 

If you can't find them that cheap near you, perhaps pick up a spark tester at Autozone.

[mihela816]

A mechanic's trick is to get a couple feet of vacuum line and cut it into ~3 inch lengths for each cylinder. You put one end on the coil post and the other end into the end of the wire boot on the coil side. Then you get a test light and ground it to the block. You touch each one of the vacuum lines with the tester and whichever one makes the least change is the one you switch.

[dohc v6]

let me get this sraight. i take vacuum hose about 3 inch long and push it on to the coil. so now i have one wire disconnected. i take the other end of the vacuum line and attach it to the end of the wire that was on the coil? next i take a test light and ground it and touch the 3 in piece of vacuum line?

[dohc v6]

ok so i took it for a drive after sitting for about 6 hours. and it was good about 2 min. i also knoticed that there is no stumble in park revving the car up

[95oldsVan]

I have a tool that looks like a pair of pliers somewhat but is designed to pull off plug boots and not get shocked.I used this to see if my coils were getting power to each one.Theres a pretty big spark from the ones that work,so use caution.

The tool should have rubber/coated handles and coated plier ends that are shaped to pull off the boots.Non conductive to say the least.

 

You may need to pull the boots off the coil packs with the car off to ensure you can remove it during the test with the car running.Some of them have been on there a long time.Pop them off then press them back on and should be easier to remove one at a time to check for voltage with the corect tool so you dont get shocked.This tool is at any good auto parts store.

 

However,another great tool to buy for diagnosing dead misfires is a timing light.You can hook up a timing light to any cylinder and hook the ground clip to the battery and watch the flashes.It simulates an engine anylyzer somewhat.You can track down weak to no spark with a timing light using it on each wire as you check,check,the firing.You can observe the flashing of each plug wire to see if its the same,or skips a beat and doesnt flash or etc for a few seconds.I found a misfire this way and it works great.

 

[slick]

However,another great tool to buy for diagnosing dead misfires is a timing light.You can hook up a timing light to any cylinder and hook the ground clip to the battery and watch the flashes.It simulates an engine anylyzer somewhat.You can track down weak to no spark with a timing light using it on each wire as you check,check,the firing.You can observe the flashing of each plug wire to see if its the same,or skips a beat and doesnt flash or etc for a few seconds.I found a misfire this way and it works great.

 

 

I've done the same as well.

[joey b]

I use the longest wire from thom the 91-95 DOHC with the footlong boot on it. Because I have moved my coils, I hold it in my hand and have a spark plug in the end that grounds out as I turn the car over. problem is I have to turn it off & connect/disconnect every time. The extra long boot assures me that I won't shock myself.

[fwdjarvis3]

Just make sure your knees aren't touching the car. It kinda hurts.

[dohc v6]

ok well i disconected ever one and cyclinders 6 and 3 no spark. what does this mean. a bad coil

[joey b]

yes, bad coil

[sdwhite]

I'd say so. New coil was $37 when I replaced mine (a couple days ago). When I needed to test my spark coil, the mechanic told me to pull all the plug wires and crank the engine. Have someone watch the spark coil terminals (and for God's sake, don't touch the GD car!)...the spark will arc between the terminals. Pretty easy to change, too but remember to disconnect your battery cable! If your 3.1 is like mine, the coils are located under the front exhaust manifold. As you f*ck around, searching for that bottom bolt holding that coil on, remember that the starter and it's HOT leads are right behind it. And, for those who are paying attention, no, I wasn't hurt but it scared the CRAP out of me.