mjd6852

Runs bad from Hot Start

My second Post. I did not get any responses from my last post, I really need help with this.

I hope you folks can help. I have a 96 Camaro with the LT1 Engine.

It has two problems that may be related.

1. It takes quite a few cranks to get the engine to start in the morning, Usually I have to Crank it for 5 seconds, turn off, Crank for five more seconds, turn off, then crank and it starts. Runs pretty good, until engine warms up, then runs better.

2. When the car has been up to normal operating tempuratures for awhile, then parked for 30 minutes to an hour, then restarted, It Starts fine, Faster than when cold, but then when I try to head down the road I get heavy misfires and it will barely run, after about 45 seconds of this it starts running better. Thens it clears up and it runs fairly normal.

The check engine light had been on due to bad O2 sensors/MAF errors, those were replaced and the light has stayed off. The "starting when hot" problem did not change though.

New data, the last time it got the Heavy misfire issue, I stuck it back on the Scanner and the only error listed was "Misfires".

The car has a Borla Exhuast so I can hear everything related to the exhuast note. It tends to Gurgle a lot when I release the throttle. I was told to replace the two "Anti-blowback" devices coming out of the top of the exhuast manifolds, does this sound like a good idea? Could these devices be causing the "Hot restart" problem also?

Thank you for any help!!!

Mike

chrism400

My car did that when the stock fuel pump was going out. Hard to start when cold, cranked for a while and even had to re crank sometimes to get it to start. Then if it was hot, and shut off for a while15-30 min, and restarted, it would misfire and hardly run sometimes for a minute or two. The pump was only putting out 22 lbs of pressure. Lean conditions are usually the culprit of backfires too so I would definitely check the fuel pressure and at least replace your fuel filter.

mjd6852

Thank you! that is one of the things that we are going to look into next!

Thank you very much for answering me, I did not know if anyone could see my post....

So yours ran really bad after the "hot Restart"?

I think mine shook so bad that it broke an exhaust hanger.

SLeePer350

DO NOT rule out the Opti. My car had symptoms that started like yours, but only got worse...if you drive it another week, maybe even another month, and it gets progressively worse, aka more backfires, no starts, etc. then you seriously want to consider this as a opti-related problem.

Note: if it is your fuel pump, I just replaced mine with a Walboro255 even though the stock was running fine. Anyway if you are concerned about installation, the pump is very easy if you do the 'trap door' method. 4 lines all with quick-connect fittings from gm. Opti swap however is MUCH MORE invovled, but is not that difficult. Good luck.

chrism400

Yes, it ran very poorly on a hot restart. It almost sounded like intake manifold backfires withno power at all. After a minute or so, it would clear up and run like a champ! At first I thought it was some kind of vapor lock problem, you know, the heat after a car has been running goes up into the intake manifold and into the heads. Just look at your temp gauge sometime. I really think it is your fuel pump - it sounds exactly the same as my problem.

Lyle A

Did you scan the PCM for any codes that may be stored?

slopokrodrigez

It's the fuel pump. It is one of the 3 main reasons for cold starting problems. Try to remember if you had run real low on fuel previously. That's a good way to kill an intank pump.

mjd6852

Hey, thanks guys. I am in the process of buying this car, (Long story). So I do not know if the thing has been run really low on fuel.

Yep, Vapor lock came to my mind also, I had not experianced since I had it happen in my 72 Chevelle, and since it's over 105 here in Phoenix, I thought that it could be part of the problem... My Temp guage was really strting to worry me, it would "touch the Orange" when in traffic, I had the DEX flushed and refilled and this is keeping the temps down, but not as low as I want. I'm going to buy a new thermostat soon, should I buy the 160 degree unit?

I love this car, so I am willing to do what it takes to get this fixed and complete the purchase, the place I am purchasing it from has done some repairs already. O2 sensors all replaced, Cleaned the MAS, Checked the Fuel filter (not thr fuel pump, this test is scheduled for Monday), (Recharged the AC) Run diagnostics several times **, etc using a Genisys Scanner (nice!)

I want to take advantage of this situation but I do not want to take advantage of them. They are willing to do the labor for free, but I may have to buy some parts if the repairs get much more extensive.

If we can get this problem fixed with the least amount of troubleshooting it will be good for both parties. Your help is greatly appreciated in this effort.

After replacing the O2 sensors the "Service Engine Soon" light comes on with "Misfires" as the only error code. (It was reporting O2 and MAS errors)

From your advice, I am going to suggest that we go after the fuel system. Boy it would be great if this is the problem and we can move on!

Here's one more thing that makes me think that it is the fuel pump. when acellerating hard in first, then shifting into Second gear, I apply power and there is a slight hesistation then it catches up and accellerates hard up to about 4500 then it seems to slightly lose power as if been slightly starved of fuel. This is not terrible but I can tell that it is not normal.

Where do I find a "Walboro255 ", Why would I want this over a Stock unit? How much should I pay for it?

Thank you again for your Sage advice, keep it coming!

chrism400

The 160 deg thermostat is a good idea if you also have either a manual fan switch or program that makes the fans come on way earlier than they are now. I have a Hypertec power programmer that I use to program the fans to come on at 170 otherwise your thermostat will open at 160 and just go up from there. http://shbox.com/1/4th_gen_tech2.html#ICM_cooling you may want to look into doing this mod too if you live in such a hot climate.
You can get the walbro from combination motorsports. http://www.cmotorsports.com/93-97-fb...tml#fuel-pumps You don't need to spend the money on the separate electric hook-up that goes to the battery.

mjd6852

Oh Yea, it seems to be fixed!!

Hey, I just got my car fixed!! All I did was replace the fuel pump. It runs soooo much better now. Every aspect has improved.

Starting, continunous accelleration,( I used to have blips in the powerband, and it would have to "catch-up after shifting into second). SHIFTING, everything is working better!!!

Wow what a difference a fuel pump makes!

Thank you for all of your advice!! You probably saved me hundreds of dollars in trouble shooting buck!

chrism400

I'm glad your problem has been solved! Now just hope that the hose you connected to the fuel pump doesn't pop off like it did for me!!!

mjd6852

I hope note also. That would REALLY suck!