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Discussion Starter #1 (Edited)
Hi, so JUST today i started having this problem:

I drove for about 20 miles with no issues, then as i started to reverse while parking the car died

I tried to start it back up right away......it was cranking, but no start

Tried again in 20 mins and started no problem

Drove another 20 miles with no issues, and parked.....went in store for 10 mins and again, car wouldn't start.....(still cranking and really felt like it WANTED to start)

Waited 20 mins and car started again with no problem

Drove 5 miles with no issues, then JUST as i was pulling into the driveway it started to sputter/die

Fuel filter was changed in spring of 2016 (roughly)

Brand new AC DELCO Platinum plugs and AC DELCO wires were put on back in 2016 too at the same time as the fuel filter

CAI filter was JUST cleaned last week

Ive never changed Fuel Pump since ive owned it.....4 years and roughly like 30k miles put on it since i bought it

Car is a 94 with roughly 60k miles in total on it.....it sits alot and only gets driven a couple hundred miles a month....

What do you guys think?

Thanks
 

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Just had a no start issue myself that was diagnosed with a very nice Step by step troubleshooting process. However, in that short time I can no longer seem to find a link that works. Glad I printed that 1 out and saved for later use. however, if you google "LT1 No start Diagnostic" you should find numerous threads on other LT1 Sites (corvette, Camaro, etc) that will have some of these steps outlined to follow.

Starting with some basics....do you at least "hear" the Fuel Pump run when you first Key on the car? It is possible the pump quit and there are numerous documented processes to follow listed thruout the forum so I won't touch on them all. Keep in mind you have the Fuel Pump override wire to use for testing too. If you suspect fuel is not your issue, get a noid light on one of the Injectors and crank the car....if it flickers then your Opti is most likely NOT the problem. You now need to move onto the ICM and follow the process for testing that.

I'm leaning toward the ICM just based on what you described.as it is a Solid state Piece and as SS gets hot and is weak it is pronbe to failure. Let it cool down and then it magically starts working again. Fairly common as the ICM gets older.
 

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The background and level of description of symptoms is relatively good. AND, you chose a good title so worth a proactive reply for hopefully future searcher(s). Problem is, as already offered there are enough perfectly likely issues to attribute your no-start that the choice will either be to use up the next week or two "watching and waiting" for the next reply with another part to throw at it - which then accidentally might turn out to be the magic bullet, OR, dig in and hit up the many many (too many) threads (some quite recent) where you can much more quickly, effectively, and most important more cheaply, get back to running.


You've probably read enough times that motors need only 3 things; air, fuel and spark. With our cars there's maybe a 1/2 dozen components required to function properly for each of those 3, but there's also readily available listing of progression of diagnostics to check in a preferred order based on 25 years of collected experience here.


Bottomline: Get an FSM - $50 and worth $500. Search here and the cosmic web for 'no-start' as recommended. The fuel side of things is already described above; FP jumper and FPR test. If you don't hear the FP then hit the tank with a 2x4 with KOIO and listen. For spark just hold a plug wire and crank it cold a second and hope for a strong bite. If not, then with your mileage more likely IC and ICM or opti harness v. opti itself. Either test the first 3 or just call them 25-year old overdue PM for $150 together. Your ETC sensor is testable with a simple VOM and really worth checking if your search finds it holds potential for involvement based on your symptoms. For air I'd be looking at that
"CAI filter was JUST cleaned last week" for anything that unintentionally got unconnected or fubared that's associated with the intake or in the vicinity of the work area. GLWS(tart)
 

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OP

my "guess" is ICM based on your symptoms. Classic for failing ICM

with that said its a good idea to rule out FP as the cause using a FPG first

some auto part stores can test ICM....but they generally test good cold but die when hot so using a heat gun on them for testing is a good idea

Use heat sink paste (some ICM's may come with a small pack of it) on the back side before mounting

I prefer AC Delco ICM. Autozone has the paste
 

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Easy tests: unplug the high voltage wire at the coil (the wire going to the opti). Crank it with your car door and hood open. You hear a nice "snap snap snap" as you crank. Or have someone watch for the spark jumping. If you see/hear that, you have spark.

Next is fuel. Spray some starting fluid or Gumout brand cleaner into the throttle body. Other carb cleaners may work, but I know Gumout works great. Crank it. Should fire up for a moment. If it does, you have fuel problems. Test the pressure. Harbor Freight sells a fuel pressure gauge set for $20. Screws right on to the schrader valve on the back of the fuel rail. Crank it and go read the gauge. Must be at least 40psi.

Finally, if you installed a CAI, make sure clamps are tight and nothing popped off. No hidden leaks. Make sure MAF is not installed backwards (I've seen that before, car will run, but not reliably). LT1 cars will run with the intake elbow disconnected AND the MAF unplugged. Won't drive well. But it will start and idle without MAF (must be unplugged). Try that too to eliminate a bad MAF or intake problems.

Using these few simple tests, I can usually diagnose a no-start on a LT1 in about 5 mins. If no spark, takes additional time to narrow it down to a bad coil, ICM, or Opti. Post back here with results.

Don't just start replacing parts haphazardly. This often makes things worse because you are disturbing things that are working just fine.
 

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Discussion Starter #6 (Edited)
Easy tests: unplug the high voltage wire at the coil (the wire going to the opti). Crank it with your car door and hood open. You hear a nice "snap snap snap" as you crank. Or have someone watch for the spark jumping. If you see/hear that, you have spark.

Next is fuel. Spray some starting fluid or Gumout brand cleaner into the throttle body. Other carb cleaners may work, but I know Gumout works great. Crank it. Should fire up for a moment. If it does, you have fuel problems. Test the pressure. Harbor Freight sells a fuel pressure gauge set for $20. Screws right on to the schrader valve on the back of the fuel rail. Crank it and go read the gauge. Must be at least 40psi.

Finally, if you installed a CAI, make sure clamps are tight and nothing popped off. No hidden leaks. Make sure MAF is not installed backwards (I've seen that before, car will run, but not reliably). LT1 cars will run with the intake elbow disconnected AND the MAF unplugged. Won't drive well. But it will start and idle without MAF (must be unplugged). Try that too to eliminate a bad MAF or intake problems.

Using these few simple tests, I can usually diagnose a no-start on a LT1 in about 5 mins. If no spark, takes additional time to narrow it down to a bad coil, ICM, or Opti. Post back here with results.

Don't just start replacing parts haphazardly. This often makes things worse because you are disturbing things that are working just fine.
Ok so its the optispark that's the problem

Therefore i'm going do this: https://www.ebay.com/itm/322692854278?rmvSB=true

Should we also change the plug wires at the same time as changing the opti ?......(i put in AC DELCO plugs and ACD wires 3 years ago, and ive put on like 30k miles since then)

Maybe just go ahead and change the ICM, and coil too while we're at this?

Im also going to need 2 new water pump gaskets (since it has to come off for changing opti) as well right?

Any other parts i need to buy/or simply just SHOULD buy when changing the opti?

Btw, I also did the "disconnect the MAF while running test": when i disconnected the MAF the car sputtered and ALMOST died when i took the harness off, but then revved right back up in a few seconds, so this means that the MAF is ok??.....that's a legit way of testing it right?

I REchecked all the connections and clamps on the CAI setup and its all tight

Any other advice/tips about what parts to get or things to do when switching the opti?

What about adding/installing some kind of "water pump drain off"......in case for some reason it might start to leak down onto the opti?

Ive looked through a few threads on the site, and ive basically listed here all the advices ive come across that im gonna need to do

But anything else you guys suggest?

Thanks
 

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How did you narrow it down to the Opti specifically?

That eBay Opti rebuilder seems to be the guy to go to these days.

As for replacing the coil and ICM, I'd like to know first how you narrowed down the Opti just to make sure your coil or ICM aren't bad. Are they both original parts? Or aftermarket? The original ICM and coils seem to hold up pretty well. The aftermarket stuff, not so much.

The way you tested the MAF is a crude test to see if it's electronically working. Sounds like it is. So as for a start/no-start, I think that's good enough.

A better way to test it is with a scan tool and watch the numbers to verify it's within range.
 
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