Popping/Extreme Loss of Power/Misfire under load?? 1989 HCI 302.

TomOsiris

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May 19, 2019
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Hey guys..

Looking for some additional opinions on an issue I have been dealing with.
Forewarning, I admittedly threw some parts into the car and did things without necessarily completing the recommended diagnosis steps in the correct order.
So with that being said I will just let you all know where I am at currently, and hopefully get some advice on how to proceed.
I'll try to keep this short and sweet as possible.

SYMPTOMS: inconsistent idle, swinging/dipping idle, intermittent EXTREME loss of power under load (revs fine in neutral), loud popping from engine bay (assume intake)

WHAT I HAVE DONE AND TESTED SO FAR: air temp sensor, coolant temp sensor, coil, plugs+wires, base idle reset, TFI module, distributor cap, fuel filter

WHAT I HAVE DONE, BUT NOT TESTED SO FAR: new injectors, matching MAF, fuel pump, fuel pressure regulator, distributor, PCV, dropped and inspected fuel tank

So basically where I'm at is I have the upper intake manifold off because I was replacing the injectors. I have been reading around a lot and have gotten about a million different answers as to what could be causing my issue, which is why I have already replaced the parts listed above.

From what I have been told popping out of the intake is due to lean condition, which is mainly caused by either vacuum leak or fuel supply.
I have replaced everything related to fuel supply but not yet tested.

This issue has sometimes disappeared for weeks at a time only to resurface, so testing is difficult.

I have not tested the car with the new injectors and MAF yet, because I am wondering if I should pull the lower intake as well?

After doing some more research I am starting to think I have a dreaded vacuum leak in one of the 2 worst places.. I have checked all other vacuum lines and they are good..
So I am thinking either lower intake manifold gasket is leaking or the brake booster is leaking internally.

My question is... do I dive into the lower intake now?? OR should I close everything up and test it with the new pump, injectors, and MAF?

I am also sending out my ECU to be inspected and repaired, however I do not necessarily believe that to be the cause of my issues.

I do almost all of my own work on this car but I am not an expert nor a mechanic so please consider that in your responses.
Thanks in advance
quiki.jpg
 
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TomOsiris

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I should probably also include that there is no CEL while this is happening, and I have pulled/cleared the codes several times with them alternating between rich codes, lean codes, and none at all.
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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Do you run a chip in the car ?

Have you cleaned and tightened up the connectors at the back of the intake ? It's the fuel injector harness connection. An issue there will cause all of the above. Take a picture of the back of all 4 ends to keep track of where the individual wires go ( white and black connectors ). Use a pic or small screw driver and pry out the red center plastic. Carefully release the tabs that hold the wires in, one by one, on the female side. Clean with electrical parts cleaner ( sold by the carb cleaner in most parts stores) Gently squeeze them shut just a little and reinstall them. Clean the male pins and reinstall. Add a little dielectric grease to the pins when sliding them back in. This gives protection against moisture and corrosion. Reconnect the connectors and it should help. Either way, it's good to do because it's a common problem for gremlins under the hood.

Another thing that's caused this in the past is moisture building under the distributor cap causing crossfire ( spark jumps to incorrect plug wires ). MSD caps had a big problem with this issue. Something about the vent cap...little cylinder thing on the top of the distributor cap. To check you can spray a little WD40 under the cap when it's acting up. If your issue clears you probably found you cause.
 

TomOsiris

Member
May 19, 2019
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Do you run a chip in the car ?

Have you cleaned and tightened up the connectors at the back of the intake ? It's the fuel injector harness connection. An issue there will cause all of the above. Take a picture of the back of all 4 ends to keep track of where the individual wires go ( white and black connectors ). Use a pic or small screw driver and pry out the red center plastic. Carefully release the tabs that hold the wires in, one by one, on the female side. Clean with electrical parts cleaner ( sold by the carb cleaner in most parts stores) Gently squeeze them shut just a little and reinstall them. Clean the male pins and reinstall. Add a little dielectric grease to the pins when sliding them back in. This gives protection against moisture and corrosion. Reconnect the connectors and it should help. Either way, it's good to do because it's a common problem for gremlins under the hood.

Another thing that's caused this in the past is moisture building under the distributor cap causing crossfire ( spark jumps to incorrect plug wires ). MSD caps had a big problem with this issue. Something about the vent cap...little cylinder thing on the top of the distributor cap. To check you can spray a little WD40 under the cap when it's acting up. If your issue clears you probably found you cause.
stock A9L

I f you are referring to the 10 pin injector connections (salt and pepper shakers) I have already taken apart and cleaned them. Sorry I didnt include that.

I have not checked for moisture under the cap, but it has happened with several different caps before and after so I doubt they would all have bad valves?

Thank you for your response.. I am stuck between putting it all back together and having not fixed the issue.. or continuing down to inspect and replace the lower manifold gasket..
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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The thing about it that puzzles me is that it does it intermittently. Usually, an intake vacuum leak will be there or it won't.

Have you swapped the distributor ?

The PIP can cause issues related to timing and its located below the rotor plate ( window wheel ).

The timing chain can cause some issues if it's worn and stretched.

Just throwing stuff at the wall....
 

TomOsiris

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May 19, 2019
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The thing about it that puzzles me is that it does it intermittently. Usually, an intake vacuum leak will be there or it won't.

Have you swapped the distributor ?

The PIP can cause issues related to timing and its located below the rotor plate ( window wheel ).

The timing chain can cause some issues if it's worn and stretched.

Just throwing stuff at the wall....
The gasket could be swelling when hot and sealing up the leak?
New distributor just went in, but not tested yet.
I would really hate to have to tear it down again if I'm already halfway there..
When I pulled the old distributor it looked fine no signs of the gear slipping or anything like that..
Believe me I've been throwing things at the wall for a few weeks now.
 
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General karthief

wonder how much it would cost to ship you a pair
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If you are this far taking it apart I would pull and reseal the lower.
You should have done the 'surging idle checklist, it would have covered all this step by step but oh well, you can still do the checklist after getting back together.
 

TomOsiris

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If you are this far taking it apart I would pull and reseal the lower.
You should have done the 'surging idle checklist, it would have covered all this step by step but oh well, you can still do the checklist after getting back together.
Thanks for your response. Before taking apart I had read through the checklist and done all that I felt would apply to my situation..
Does the lower gasket seem like it could be the culprit here?
It seems to me like an intermittent vacuum leak and the only places it could be are lower gasket and brake booster
 

Boostedpimp

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May 8, 2003
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what kind of vacuum readings were you getting at idle before you tore it apart? Fuel pressure steady? no code 21 present? compression check or at least a cylinder balance test comes to mind if it were my car just throwing that out there
 

TomOsiris

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what kind of vacuum readings were you getting at idle before you tore it apart? Fuel pressure steady? no code 21 present? compression check or at least a cylinder balance test comes to mind if it were my car just throwing that out there
code 21 ect out of range? no didnt get that
replaced ect sensor anyways while I was in there
I did not check vacuum with a gauge although looking back I should have before I tore into it.
compression test would tell me if I was looking at a blown head gasket or a bad valve, but I don't suspect either of these because it seems as if the whole engine is missing not just one cylinder, if that makes sense.
The problem also comes and goes like a lightswitch. Sometimes goes for weeks without any sign and then its back..
Usually clears up in a few seconds of WOT but the last time it happened all the way home for like an hour.
 

Boostedpimp

15 Year Member
May 8, 2003
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code 21 ect out of range? no didnt get that
replaced ect sensor anyways while I was in there
I did not check vacuum with a gauge although looking back I should have before I tore into it.
compression test would tell me if I was looking at a blown head gasket or a bad valve, but I don't suspect either of these because it seems as if the whole engine is missing not just one cylinder, if that makes sense.
The problem also comes and goes like a lightswitch. Sometimes goes for weeks without any sign and then its back..
Usually clears up in a few seconds of WOT but the last time it happened all the way home for like an hour.
The intermittently piece is the key here.. how long until you get your ecu back to try?
 

TomOsiris

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The intermittently piece is the key here.. how long until you get your ecu back to try?
hopefully not too long, just shipped it today and they say it only takes a few business days turnaround..
I'd estimate about 10 days before I see it back
 
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DOHCtor

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May 23, 2004
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After you try the ECU, you could do a leak test on the booster by pulling vacuum on it, and a smoke test for engine vacuum leaks - or the old spray can around the gasket joint method, which is somewhat dangerous. Use at your own risk. The intermittent condition seems more electro mechanical to me. Bad grounds and faulty shielding in the injector harness can cause this issue. A bad MAF connection or dirty MAF sensor is worth investigating, even though the MAF is new, Pretty sure some of this has been touched on already. I would also check to see if the car has this issue with a low, versus 3/4 tank of fuel. I'm not sure I read whether you changed the coil or not, but they can give headaches like this. Also check fuel pressure when this problem is happening.
 

DOHCtor

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May 23, 2004
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I just thought to add that you can "wiggle test" different connectors / places along the wiring harness, while the engine is running.
 

TomOsiris

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I just thought to add that you can "wiggle test" different connectors / places along the wiring harness, while the engine is running.
I imagine this would be pretty difficult while driving! keep in mind this only happens under load and there are no symptoms in neutral
 

TomOsiris

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May 19, 2019
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After you try the ECU, you could do a leak test on the booster by pulling vacuum on it, and a smoke test for engine vacuum leaks - or the old spray can around the gasket joint method, which is somewhat dangerous. Use at your own risk. The intermittent condition seems more electro mechanical to me. Bad grounds and faulty shielding in the injector harness can cause this issue. A bad MAF connection or dirty MAF sensor is worth investigating, even though the MAF is new, Pretty sure some of this has been touched on already. I would also check to see if the car has this issue with a low, versus 3/4 tank of fuel. I'm not sure I read whether you changed the coil or not, but they can give headaches like this. Also check fuel pressure when this problem is happening.
Thanks for the response, I have decided to put everything back together and see how it goes.. who knows maybe it will be good for another few weeks without showing up again! I have spoken to a local mechanic who is willing to pull the lower intake manifold for me if needed.
 
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horseballz

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Though I know next to nothing about EFI, the one thing I have heard repeatedly is that proper ground connections are pretty much the most important piece of the puzzle!
Just My $.02,
Gene
 
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AydenTv

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Fuel Pump... Mine did same thing.. is yours loud... and does it drive fine and then act up and feel like dying... until your turn it off and recrank it... also if you have a cold air intake make sure it isnt a hot air intake, and is your firing order 15426378 or 13726548... it can look like a 5.0 ho motor and be a non ho.. will not hurt to test this by switching to the firing order you dont have...
 

DOHCtor

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May 23, 2004
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I imagine this would be pretty difficult while driving! keep in mind this only happens under load and there are no symptoms in neutral
Sorry, I missed the part about it only happening while driving / under load. Yeah, that would make the wiggle test a little harder, LOL.