My '89 has developed a pretty good miss, feels like a dead cylinder miss, not a hard, intermittent ignition miss. I replaced the plugs, wires, cap and rotor, but it didn't help. The plugs all looked pretty much the same. It seems to be worse when the engine gets to operating temp. I unplugged each injector wire, and the #3 cylinder seems to be the culprit. No change in rpm. #7 gives a barely noticeable change also. Oddly, when I unhook #8, the rpms come up! I tried swapping the wires to #s 3 and 1, but the problem stayed with #3, so that rules out the wiring. Same with #5/7 and #6/8. So it appears wiring is not the problem on any of them. I also disconnected the plug wires on 3, 7 and 8, with the same results as pulling the injector wires. So now I'm pretty confident the injectors are the problem, but does anyone have any other ideas or possibilities that I'm not thinking of? Thanks!

 

Disconnecting any wire or unplugging a single injector isn't a meaningful test as the ECM maintains Targeted RPM via the IAC. You can isolate a cylinder by using some 1 inch pieces of vacuum hose inserted between the plug wires and the Distributor Tower and then touching each wire with a grounded test light which will kill the cylinder. Being that you have an '89, I'd simply check the #7 cylinder for a weeping head gasket. Pull that plug and compare it to #5 to see if it's cleaner or conduct a leakdown test.

 

Even though #3 seems to be the problem? Why do you say #7? Thanks again!

P.S. I forgot to mention, I did a compression check and all cylinders had between 165 & 185 psi.

P.P.S. Also, when unplugging the injector wires, #'s 1, 2, 4, 5, 6 each had a very noticeable drop in rpm, while #7 was only slightly noticeable. #3 was no change and #8 actually had a rise in rpm. And I did this repeatedly so as to be sure it wasn't a fluke.

 

Anyone else??

 

Sounds like you need to do more trouble shooting. I would first do a fuel pressure test.....then ohm check the injector(s) cold be you have a weak injector coil. You may want to buy or borrow a noid light....cheap tool that comes with many adators.

I went thru similar things with my 87...did all the checks...ended up being a bad pigtail at the injector.

I'd certainly recommend doing a thorough check before throwing parts at it.

 

Thanks Rick! Wouldn't I have already ruled out the pigtail when I swapped them between 1 and 3, and the problem stayed with 3? As for fuel pressure, wouldn't I see problems with all cylinders, not just one or two? I will check the resistance for sure before doing anything. I'll also double check the fuel pressure.

 

Speeding up after pulling #8 seems like #8 is pulling the other injectors down. I'm not positive about your year but mine fires all four on the same bank at the same time. In other words there is only two outputs to fire all eight injectors. Four injectors per output. If it speeds up when you pull #8 then that injector is probably bad in some way probably low ohms or shorted. By pulling it you let the other three fire correctly therefore speeding up your idle. Try taking #8 off and going for a short ride. If the missing gets less then replace #8 and your good to go.

 

It isn't a fluke - Electronic Fuel Injection controls idle via the IAC and pulse width, relying on whatever number is burned into the ECM - referred to as Targeted RPM. Disconnecting any injector or plug wire just raises one if not both to come to the Targeted spec. Injectors are tested by measuring the pressure drop which you do by pressuring the rail and with your pressure gage attached, energizing each injector for 5 ms and observing the drop on the gage. They should all be within 10 psi of one another. That takes a special tool which NAPA use to sell for something less than $100. More enterprising souls have removed the rail with the injectors attached and used a measured beaker under each to determine the flow.

I mentioned #7 as it's longstanding problem with the 113 head on all Years that use it, though '91 is a redesign before it was dropped. Complaints were plastered all over the NHTSA site for a number of Years, GM was sued several times for warranty denials, and a Bulletin was finally issued about the redesign. The gasket weeps coolant at that hole (more often than any of the others), you seldom see it on a compression test though a leakdown test often picks it up and a Scan will show it's compensating for a Lean Condition which is what a small amount of moisture does to combustion. A less than perfect idle, loss of top end, crappy looking coolant, high coolant temps, plugged up radiators and heater cores are other clues. The good news, if there is any, is that most were crapped out by 50,000 miles. The bad news is that it can wear a groove into the deck and if someone fixed it without fixing that groove (assuming it had one), you're forever replacing the head gasket and chasing the above issues.

 

I had a bad injector connector with a cracked conductor, if the injector connectors are pulled by the wires that will do it.
You can buy a new electrical connector they are cheap, you can also try plugging the no1 injector connector on no 3 as a test. (all the injectors fire at the same time)

 

Does your car still have the original injectors? If so, as another forum member indicated, ohm check them when the engine is cold and again when its hot. They should be reading about 14 or 15. If you have any reading 6 or under, that may be your problem. The original injectors were not made to handle ethanol. It breaks down the seal and they short. If it is the injectors, do yourself a favor and replace them all at the same time.

 

Well I finally got around to ohm-checking. Cold, #s 3 & 8 were about 10 ohms, #7 was 15, the rest were 16. Hot, 3 & 8 fell to 2.5! 7 was also down to 6.5. Maybe new injectors needed? ;-)

 

I thought you would find low ohms on #8 maybe even shorted. Yes I think its new injector time also. I just ordered a set of the Bosh III's from Jon (FIC) and they arrived in a couple of days. Great price. May be doing them this weekend. The last project this year and then on to enjoying the ride for a while.

 

Just thought I'd update...I ordered a set of Bosch IIIs from Jon at FIC, installed last weekend. It was much easier than I thought it would be. I followed SamLam's process and didn't loosen the runners, worked great. New injectors make it run nice and smooth, and no more idle hunting! I also cleaned the MAF and TB, so that might have something to do with it. Only problem now is with the pressure. When I pressurize the system with key on, it comes up to about 37-38 lbs but drops off, so now I've got to do some more troubleshooting to see what the problem is there. Hopefully it's a bad pump rather than a leaky injector. Thanks for all the help everyone!

 

If you don't have the Factory Service Manual(s) I suggest you buy them. TROUBLE SHOOT before throwing $$ at it. Check your fuel pressure regulator and fuel return line first. You can pinch off either line to see if that stops the pressure loss. Signs of a bad regulator are raw fuel in the vacumn hose.

BTW....how much pressure did it lose? and how long did it take for the pressure to drop?

 

I think you need to buy the FSMs, factory service manuals. You can trouble shoot the pressure loss by first checking the fuel pressure vacumn line for raw fuel.....if none pinch it off and see if the pressure still drops. Next you can pinch off the fuel return line...once again see if the pressure drops. No use replacing the fuel pump if it's the regulator or vice versa.

You've already done the rest. BTW, how much pressure did you lose, and how long before it dropped?

OOPS, sorry for the double post.

 

I found a pdf of the fuel system troubleshooting steps, so I'll take it step by step to determine the issue. My dad has the FP gauge, so as soon as I get it back I can start on it. I don't remember exactly how much pressure it lost after initial pressurization, but it was a steady bleed-off. I also don't remember what the pressure was at idle. I was just happy that it started and idled smoothly lol! I just want to get the fuel delivery system ironed out so I can move on to the next problem, cooling this damn thing! I want to be able to use the A/C without it overheating!!! The new radiator helped but the temps are still too high with the A/C on. Call me old school, but I really don't like coolant temps over 210.

 

Ok so the fuel pressure comes up to 43psi during the 2 second initialization, then drops steadily to 0 within about 2 minutes with the key on. Pressure at idle with vacuum line unhooked is 45, put vac line on and it drops to 37. Nice and steady pressure no matter what rpm. So I started the troubleshooting steps, with step 1 being to pinch the flex fuel line to see if the pressure drops. Problem there is, how are you supposed to pinch it? It's metal, isn't it? Won't it kink or collapse it if I do that? I tried with vise grips and medium force but it didn't seem to pinch it at all. Is there a trick to doing this? Thanks again for any help!

 

BTW Rick, there was no fuel in the vacuum line. Regulator and injectors are brand new from FIC, so while that doesn't mean they can't be the problem, I would first think pump or cold start valve maybe?

 

If the fuel pressure drops off to zero within 15 minutes after shutting off the engine that's usually a leaky injector.

You pinch the return line at the tank. There are rubber hoses there that connect the steel lines to the tank. The usual method is to use vise grips. I guess you could pinch the rubber hose at the front of the engine, but I suspect it would be difficult to get to. There are rubber fuel lines at the bottom right front of the engine that connect the steel fuel lines attached to the frame to the steel fuel lines at the front of the engine that connect to the fuel rails.

There is a check valve inside the fuel pump that can be leaky. As long as pressure stays up while the engine is running then it's not a problem.

'89s don't have a cold start valve.

It's quite common for these cars to run as high as 230° on hot days with the A/C on. Not a problem.

Mine's usually around 210° to 220° on "normal" days without the A/C.

 

Man I hope not, since they are brand new!

Thanks, I was confused on where to pinch the lines lol.

That's what I was thinking. If it is the pump, what difference does it make if it bleeds back into the tank when you pressurize the system, as long as while the pump continues to run it maintains proper pressure?

Thanks for that bit of info.

230 just seems so hot to me, especially with aluminum heads, and also especially when considering the thing runs at 180-185 without the A/C on during 100 degree weather! I would just feel better if I could keep the temps under 200 with the air on. Thanks again