TPIGroove Posted June 18 Share Posted June 18 Hello all. 1988 year, 134k-ish miles. Water pump squeaks, and the engine stumbles something fierce under light acceleration (just off throttle). Already upgraded the coils to the newer style. Stumbling only seems to happen in hot weather, it did something similar last year, although not as bad. I'm not entirely sure if the CPS is the issue, but honestly come this 4th of July weekend I'm gonna just replace the water pump, harmonic balancer, CPS, and do the timing chain while I'm in there and hopefully that'll at least make life easier on the engine and eliminate one possible issue. The mileage is near enough to justify it, anyways. Biggest thing is I'm looking for a list of all the parts I'm gonna need. I already got the Bosch water pump and gasket, but for the other stuff are there good recommended places to get parts? Does anyone have a rundown of everything needed for this? I checked NAPA for the balancer and they sell it without a new bolt, is the bolt a torque to yield or is it reusable? Also, I read something about the timing chain having a wear part that was fixed in later years of the engine. Should I worry about the cam magnet as well? I read the guide on it, but the P/N listed seems to be out of stock everywhere. Link to comment Share on other sites More sharing options...
2seater Posted June 19 Share Posted June 19 It used to be easy to walk into any auto parts store and get what you need but not so much today, The LN3 was discontinued in 1990 and while similar to the Series 1 there are some small differences. You will want a gasket set for the timing cover, which should have not just the case gasket but also a new crank seal, new o-rings for the heater pipes and maybe one for the oil filter adapter but that can stay in place when the cover is removed. Definitely replace the magnet if doing the timing chain set, also called an interrupter. Replace the formed water bypass hose which connects the intake manifold to the water pump area. There is no reason to replace the harmonic balancer unless the rubber face is getting cracks in it or missing pieces. Yes, replace the CPS. The timing chain set is up to you, but I have always recommended the genuine GM part, chain made by Morse, due to the smoother top surface which rubs against the plastic chain damper. Be sure the chain damper is the correct one, not just the style. There is one for counter-bored and chamfered bolt holes. Usually the chamfered is the correct one. In case it comes up while gathering parts, it is a three bolt cam. 2 Link to comment Share on other sites More sharing options...
TPIGroove Posted June 19 Topic Author Share Posted June 19 I was reading about the tensioner, are there casting numbers I can reference? I get the feeling if I grab the wrong one, getting the right one will be impossible on short notice. Balancer is cracked, so he's coming off. Would I need a puller? I know it's just the bolt holding it, but I doubt it'll slide off easily. Link to comment Share on other sites More sharing options...
2seater Posted June 19 Share Posted June 19 No casting numbers I know of. As a matter of fact the block for the S/C engine in my car now is an 88 and I used a chain damper for a chamfered bolt hole. Balancer should not require a puller. Sometimes it requires a little help but not a puller. The bolt is reusable. A little medium strength (blue) Loctite on the threads on assembly. 1 Link to comment Share on other sites More sharing options...
TPIGroove Posted June 19 Topic Author Share Posted June 19 I just thought about it, do I need to remove the oil pan to get the timing cover off? Link to comment Share on other sites More sharing options...
2seater Posted June 20 Share Posted June 20 2 hours ago, TPIGroove said: I just thought about it, do I need to remove the oil pan to get the timing cover off? There are three bolts from the pan into the timing cover. It does help to loosen the pan to allow a bit of clearance where the pan gasket and front cover meet. You do not need to remove, but all of the bolts down the sides need to be loose to get the pan to drop at the front interface. 1 1 Link to comment Share on other sites More sharing options...
2seater Posted June 20 Share Posted June 20 I found a photo on my phone of what the completed timing set replacement looks like, including the new style chain damper. Also a photo of the bolt used on the original chain damper which I have been looking for. 1 Link to comment Share on other sites More sharing options...
TPIGroove Posted June 26 Topic Author Share Posted June 26 (edited) Parts all came in yesterday. I went ahead and ordered two tensioners for each style, together from rockauto they were the same price as one from the chain auto parts stores. The only difference I noticed was the threaded bolt was either longer or shorter. I actually had a bigger issue today. The misfires were particularly violent this morning, so much that driving to work on the highway the engine would miss very bad and buck the whole car back a bit. It's been very hot lately, and yesterday was bad until the rain rolled in. I noticed she was running rougher than normal as I pulled up to my house and parked, but I figured it would go away once it sat overnight. Come the morning and it's running terribly, I was worried I'd be stranded at work. Started the car up to get home, and while the occasional stumbling just off throttle was still there she ran relatively fine regardless, same as she has been the past month or so. The drive back had me think of something similar happening last year. It was in hot weather like this, around 95-100F outside temps. After fighting stop and go traffic she was running a little rough, so I stopped somewhere to let her cool a bit and let traffic dissipate. Started her up and she was bucking like this time, so I immediately shut her down, then tried to start again. The bucking was gone after the restart. On top of that, my stumbling has only happened in hot weather, it goes away in all the other seasons. Once it gets to the 70s/80s it starts up, and gets worse the hotter it is outside. I'm not entirely certain replacing the cam sensor will fix this, is there another possible cause for this issue? I've already upgraded the ignition coils to the newer style, and even checked the ones I have on there now for good measure. Pulled codes and nothing from the ECU indicates this is a problem. Edited June 26 by TPIGroove Link to comment Share on other sites More sharing options...
2seater Posted June 26 Share Posted June 26 I agree the cam sensor is unlikely to fix this issue. Heat related issues are usually ignition. If you are comfortable the ICM and coils are not the issue, that leaves the crank sensor, but the symptoms are unusual. The other thing that comes to mind is the fuel pump doesn't like the heat either. I don't know if it is possible to vapor lock a pressurized system, but I would suggest checking the pressure when it acts up. 1 Link to comment Share on other sites More sharing options...
Anthony Posted June 27 Share Posted June 27 I've had several MAF sensor failures that caused the same problem. Pushing the pedal very slowly would allow it to get back home, but there was very little power for getting up hills. If I remember correctly, unplugging it would force the computer to use a default value. 1 Link to comment Share on other sites More sharing options...
TPIGroove Posted June 27 Topic Author Share Posted June 27 (edited) Would the MAF not throw a code in those situations? It started it again today, getting lunch at work and fighting stop and go lunch rush traffic, just 10 minutes of throttle on-off and it was missing even in neutral at a stop. Very light throttle would be smoothish, but not much else. I just pulled the MAF wire and it was still stumbling the same as before, although the burnt smell was immediately noticeable. No burnt smell normally. The transmission shouldn't affect the engine in neutral/park, correct? Are there any vacuum lines that regulate the fuel? Edited June 27 by TPIGroove Link to comment Share on other sites More sharing options...
2seater Posted June 27 Share Posted June 27 4 hours ago, TPIGroove said: Would the MAF not throw a code in those situations? Are there any vacuum lines that regulate the fuel? Any sensor can malfunction but not to the point of setting a code. Essentially, it can give bad info which may be worse than no information. Sort of why we recommend disconnecting a suspect sensor to see what if anything changes. This can be done for almost all sensors except the CPS and possibly the TPS. There is a vacuum line at the front of intake manifold that connects to the fuel pressure regulator at the front of the fuel rail. Pull the line and check for fuel in the hose. Any wetness indicates unmetered fuel into the intake. 1 Link to comment Share on other sites More sharing options...
TPIGroove Posted June 29 Topic Author Share Posted June 29 Well, I'm pretty sure it's a fueling issue now... She stumbled pretty bad Thursday and I barely limped her home. Borrowed a car to get to work, then took a look today. Family member needed to move it around the block for something, it barely even started. When I went to take a look, figured I'd see if a new code came up, but turning the ignition I very definitely don't hear the hum of the fuel pump. Get a new unit, or is it rebuildable? Link to comment Share on other sites More sharing options...
DAVES89 Posted June 30 Share Posted June 30 I'm a pretty simple guy, don't use the manual, hardly go for codes, just do basic stuff. For fuel I take the cap off the fuels Schrader valve and press it with a screwdriver. If it givese a good squirt the fuel system is good. You talk about the cps, is that the cam position sensor or the crank position sensor. The cam position sensor only allows the car to run at factory specs. It will not give the hard running issues you describe, but the crank position sensor will. Try replacing the crank position sensor and tell us what happened. 1 Link to comment Share on other sites More sharing options...
2seater Posted June 30 Share Posted June 30 I know Dave eschews instrumented help, and is pretty successful doing so, but he is also very experienced😁 I do lean more toward getting actual numbers. Nominal fuel pressure with engine running and vacuum line connected is ~35psi, so a good squirt from the Schroeder valve could shoot a stream dozens of feet in the air, a wet dribble won't cut it for starting or accelerating. Fuel pump is commonly available as a replacement part, not repairable. 1 Link to comment Share on other sites More sharing options...
radride90 Posted July 2 Share Posted July 2 i had all those same symptoms and it was the crank sensor- just did it saturday it’s now running perfectly Link to comment Share on other sites More sharing options...
TPIGroove Posted July 4 Topic Author Share Posted July 4 The misfires suddenly getting worse turned out to be one of the coils going bad, which is pretty bad after barely a year of use. Still stumbling though, so really it's just when I have the time to do the work. Link to comment Share on other sites More sharing options...
2seater Posted July 4 Share Posted July 4 11 hours ago, TPIGroove said: The misfires suddenly getting worse turned out to be one of the coils going bad, which is pretty bad after barely a year of use. Still stumbling though, so really it's just when I have the time to do the work. My unscientific observation of the two styles of ignition packages is: the Magnavox type has more issues with overheat and melting of the potting material in the ICM, on the other side, the Delco style has more coil failures. The Delco style does produce a more energetic spark, which has been demonstrated in the past, but coil failure may be the side effect. In any case, I have heard recommendations that the coil(s) be replaced at the same time as the ICM in both styles as a defect in one part of the package can overstress the mating piece. I know I have never done so, but then I have changed engines in my car a half a dozen times so my experience is not the norm🙃 1 Link to comment Share on other sites More sharing options...
wufibugs Posted July 5 Share Posted July 5 You should be able to borrow a fuel pressure tester from AutoZone or similar and determine if you are getting enough gas at the rail. If not, I can tell you replacing the fuel pump without at lift is a cheap but nasty DIY job because the tank has to be removed to get to the pump. I haven't reviewed the whole post for this reply, but I assume you changed the fuel filter already. You could also be having injector issues. I recall replacing the entire rail and all the injectors from a salvage yard car with good results. Link to comment Share on other sites More sharing options...
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