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Discussion Starter #1
My sons '88 Caprice with 305/4bbl has not guts.
It starts fine, runs fine, but once it warms up, it simply has no umpfh.

All of these computer controls are driving me crazy.

I am looking for suggestions. Once warmed up, you can give it gas but it is just very slow to accelerate.

On the same subject, how difficult would it be to bypass the electronic and just run an HEI and quadrajet? Ohio has eliminated their sniffer test. I'm afraid to let him take this thing on a trip as he'd get mowed down on the highway, also, the milage is lousey.

We have aleady replaced the cap, rotor, wires, fuel filter, PCV, air filter, and breather. the carb is electronically controlled. It seems to make no difference whether the plugs to the carb are connected or loose.

Does anybody understand these controls?
 

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Dan, does the check engine light come on? How many miles are on it? Has the cat ever been replaced? It sounds like it could be a plugged cat.

Randy
 

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Discussion Starter #3
There are 130,000 miles on the car.
The check engine light does not stay on, though there may be codes set.
I will double check that tomorrow night.
Tonight we tried to check the fuel pump volume. we disconnected the fuel line at the carb, connected a line extension and ran it to a container. We never could get much more than a trickle running into the container. It strikes me as low, but I do know it will draw a vacuum on the fuel tank.

We then disconnected the line going into the pump and ran that to a container with gas in it. The carb was reconnected. The engine fired and ran ok. By OK I mean the same way it has been running. I guess pressure could be marginal and that could make it run sluggish, but once warmed up, it really doesn't want to speed up when you try to accelerate.

The guy we got it from made some comment about the engine having been replaced, so now I even have some question if everything is even connected properly, but it sure seems to be.

I'm really stymied on this one. That is why I am considering bypassing all of the extra stuff and working forward from there. Any guess what would happen if I put in that HEI but still tired to run the electronic carb?
 

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I doubt the problem is related to the carb or HEI. For what it's worth, a friend of mine had a Caprice like that and it got 24 mpg highway. Not a real powerhouse, but it ran fine.
 

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Discussion Starter #5
That is what I am looking for is the 24MPG on the highway. Just checked a tank and it got 10 PMG around town. I am not looking for super performance, I am just looking for the engine to not nearly die out when the trans makes the 1 - 2 shift.
 

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I'm wondering about the fuel filter being plugged. is it a carb with a mechanical pump? ( sorry i've got a 90 w/350 ... throttle body injection & electric pump and want to make sure what you're working with)
If it's the mecanical pump i wonder if the pump's weak. any pump should give you a good healthy shot of fuel thru an open line.
 

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I wouldn't expect any better than 13 mpg around town, so 10 is low.

Even though the carb has wires going into it and the distributor is controlled by a computer, those engine controls are not that complex. As long as you have fuel, spark, and compression it should run.

GM computer controlled distributors are very reliable so I doubt that is your problem. I believe you replaced the coil when you were troubleshooting problems several months ago???

I've never heard of a modern engine losing so much compression that it would not run. So I doubt that is your problem.

That leaves fuel. It would seem, based on your fuel pump observations, that fuel pump output is low. You should be able to install a new Napa pump for under $20. If you do, don't buy their cheapo "tru-flow" pump. I put one of those on my old Caprice and it was running 9 psi fuel pressure. It also would not leak down when I shut off the engine; causing it to flood.

Although I am not 100% certain, I believe the wires going into the Q-jet have something to do with it maintaining 14.7:1 air/fuel ratio from the oxygen sensor. If you unplug these wires I expect it would run rich, but I'm not sure. I friend of mine unplugged them on a 350 years back and it seemed to run fine. It's possible somebody has set the float level way low in that carb for some reason.
 

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Discussion Starter #9
Thanks for the suggestions. I bought a new fuel pump last night and will probably replace tonight. If that isn' it, I considering seeing if I can disconnect the cat converter to eliminat that as a suspect.
 

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Dan, does the check engine light come on while the engine is running? If if comes on while the engine is running, even if it goes out, you have codes set. I think there is a procedure that will allow you to retrieve the codes without the use of a scanner. I tried to find the procedure with a quick google search, but came up with nothing. I am not sure how much the computers were changed from 81 - 88, but on my 81 El Camino, there is a diagnostic connecter under the dash. When the proper 2 connectors are jumpered, the check engine light will flash the codes. Maybe even somebody here will know which connectors to jump. Once you have the codes, and are able to determine what is causing them, it may save you a lot of tail chasing time.

As time permits, I will do some searches.

Randy (NPHNP):)
 

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Check you base timing. You will need to bypass computed timing and you can find out how by reading the directions on the emissions sticker. If the sticker is missing check a service manual or I can get the info for you. Also pop the cap and rotor off and inspect the pickup coil. Check the trigger ring that is pressed on the distributor shaft. This ring can develope a crack in it which will cause it to shift position on the shaft. The engine will still run but the timing will be off and you won't see this with a timing light. I have seen these crack in a fashion that you visually can't see the crack but you can push the trigger ring with a screw driver to see if it is loose. This is common problem that throws a lot of people for a lupe if you don't know about it.

Also try dropping the exhaust and see if the lack of power goes away. It only takes 3 psi of back pressure to cause major performance issues.

Check the fuel filter in the carb. If it is installed backwards you will have problems. Be carefull tightening the fuel nut you can crack the carb body pretty easily.

Frank

Frank
 

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One more thing the MC Solenoid can also cause your problems, but I recommend you take it to a professional. These carbs are tricky to adjust and I don't recommend someone of inexperience messing with them. It will only cost you more money in the long run.
 

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I drive an '84 caprice everyday. It has the 305 4bbl and a 700r4 and that thing is a dog in terms of performance, you have to about floor it to go up a hill. However it is the most reliable v8 I have ever driven. It has over 275,000 on it and it still starts even when it is -10 degrees out. I guess this really has nothing to do with the post but I have already typed it so I am going to post it any way.
 

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Discussion Starter #14
We reset the codes on Tuesday night. My son drove the car to work and back yesterday. Last night we jumped the terminals per the manual and there were no stored codes!!! much to my surprise...... We had checked the fuel pump for pressure and volume on Tuesday night and I was surprised by how little pressure there was, then I realized we may have only had a quarter tank of gas. We bought a new fuel pump and some rubber fuel line that night. Last night after checking the codes and finding none. We rechecked the fuel pressure. Still appeared low so we went ahead and changed the fuel pump. Took the car for a short drive and I thought it was considerably better. I am waiting for my son to get home so I can get his impression after driving it in traffic. I am thinking the carb probably needs a zip kit too. I'll post his comments when I get them.
 
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