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MasterJax 12-22-2015 08:22 PM

1996 2.3 Engine Bucking under load
Some of you might have seen my last thread "PCM Fuse Keeps Blowing". Now that my truck is running again I'm still getting an awful misfire under load, such as climbing hills. But on flat ground, or if I shift into a lower gear it quits bucking. This is a shame because I really thought my most recent tune-up would have fixed this issue.

Any insight would be appreciated!

mxpxpunkrock1987 12-22-2015 08:37 PM

Re: 1996 2.3 Engine Bucking under load
check compression and timing and check timing sync also how many miles are on the motor as these engines get older the exhaust side on the 4 cyl are know for blowing the seating ring causing the bucking i have a 94 i redid the motor and runs like day 1 all new my second project is my 96 ranger which has 220,000 and is just starting to do the same thing and a loss of power

MasterJax 12-22-2015 10:03 PM

Re: 1996 2.3 Engine Bucking under load
Is the seating easily replaceable, or do I have to start pulling the engine apart starting with the valve cover? Also, what causes this misfire? Is it a loss of compression due to an air leak?

MasterJax 12-23-2015 09:00 AM

Re: 1996 2.3 Engine Bucking under load
Should I try replacing the Camshaft Sensor?

MasterJax 12-25-2015 07:40 AM

Re: 1996 2.3 Engine Bucking under load

GSF1200S 12-25-2015 01:19 PM

Re: 1996 2.3 Engine Bucking under load
Under load... first thing that popped into my head was coil pack, though I suppose wires or plugs could do it too. Since you have a lima, try swapping your coil packs. IE, you have two coil packs under the hood- one fires the cylinders for power, and the other is to help emissions by firing to burn off remaining hydrocarbons on the exhaust stroke. Swap these coil packs- put the one currently firing on the compression/power stroke as the exhaust coil, and vice versa.

With that many miles, if the coil packs havent been replaced, they really really need to be replaced.

You could also try disconnecting the MAF and going for a drive- see if the problems remain. If the MAF is reporting the wrong flowrates it will manifest in all sorts of strange ways.

Finally, I would check your fuel pressure. When was the fuel pump and fuel filter last replaced? Again, if the fuel pump is OEM its very likely the cause. If the fuel filter hasnt been changed in 30-50k, it could also be the cause. You can rent a fuel pressure gauge from autozone or advance and connect it to the schrader valve on the fuel rail- you should have a reading of AT LEAST in the 50s psi, and preferably up around 65psi. If you have more (like 80psi or whatever), you could have a bad fuel pressure regulator flooding the engine, but youd likely see that in your gas mileage, black sooty pipe, carbon fouled plugs, etc..

Try the above and let us know what you find- it will help us narrow down the cause.

MasterJax 12-25-2015 06:12 PM

Re: 1996 2.3 Engine Bucking under load
Thanks for your reply. As noted on the other Thread, I've replaced Ignition Coils, Spark Plugs, Fuel Filter, Fuel Pump, Fuel Injectors, and replaced all vaccum lines. I haven't tried your MAF Sensor test yet, but I will give that a shot to see if that could be the problem. I will be cleaning the MAF Sensor once the shops open up again.

tomw0 12-26-2015 09:13 AM

Re: 1996 2.3 Engine Bucking under load
I did not note plug wire replacement. They can leak the voltage to the block or cam cover, or to each other and cause misfire, especially noticeable when under load.
Try running the engine at idle, after dark. If you note a 'light show', time for plug wires. They can also cause misfire when it is more humid than normal if they have deteriorated.

2006_FX4 12-26-2015 09:28 AM

When I recently change my plugs and wires I had a bucking/misfire problem. My CEL wasn't flashing at first( it eventually started to) when the light came on I pulled my codes and there was a specific misfire. Pulled that plug and it was cracked. Didn't notice the crack coming out of the box, didn't drop it, didn't over torque it. Talked to my mechanic buddy and he said that boxes get dropped all the time during shipping and my plug was prolly dropped at some point, if I didn't drop it myself, leaving a hairline crack. Id try pulling codes and replacing wires before delving into fuel issues and compression and timing.

MasterJax 12-27-2015 01:30 AM

Re: 1996 2.3 Engine Bucking under load
Thanks for the replies, you guys! To answer an earlier question I changed my plug wires as well so that shouldn't be the root of the problem.

I had my timing belt done recently and the mechanic who did the job said my belt tensioner was worn out, he didn't replace it though because he felt like it "wasn't that bad". Could this have caused the problem? Or could the misfire be from a bad CPS? I also haven't replaced the EGR Valve... could this possibly be the cause as well? Do EGRs suddenly go bad without warning? I haven't had a check engine light for this issue for well over 5 months.

Also to note, my most recent timing belt change is still covered under warranty so I'm planning on having it back in the shop by Monday(If this 2ft snowstorm chills out, pun intended!). I'm also having them perform a diagnosis on the Misfire.

I'll let you guys know the outcome.

MasterJax 12-31-2015 01:53 PM

Re: 1996 2.3 Engine Bucking under load
After dogging my truck today and becoming really excited after seeing a CEL finally appear.(my girlfriend thought I was crazy) I took it over to Autozone and had a them run the codes and I received error code P-1443 For EVAP Canister Valve mechanical or VMV fault condition.

This truck has failed it's emissions test twice before I got a hold of it. The original owner did something to fix it(I don't know what) and it somehow passed.

My question is;
Could a bad EVAP pressure sensor, or vacuum leak heading to the canister cause a misfire? If that's not the case, could a bad EGR Valve cause the misfire at lower RPMs when put under load?

Thanks for your comments!

tomw0 01-01-2016 07:59 AM

Re: 1996 2.3 Engine Bucking under load
The canister valve just allows fuel fumes from the gas tank that have been stored to vent into the intake and burn instead of venting to atmosphere. It should not affect running except if it was bleeding air into the intake.
The EGR should not be applied at idle, and if it were, the idle would be lumpy with misfire and perhaps stalling.
If you have bucking, you can look to plugs & wires, the EGR feeding too much as noted, and fuel supply. If you have a bad valve seat (mentioned previously) the engine would misfire all the time, or at least have a very noticeable intermittent at idle. The valves wear the seats and cause 'recession' where the valve goes further and further into the cylinder head seating area. Cure is removal and machine shop work to replace the seat, or re-man/used heads.
When you have a low speed miss, look for mechanicals, as they cannot be hidden as well by increased rpm. High speed misses and bucking tend towards ignition and fuel problems. EGR optional and not so much.

MasterJax 01-01-2016 02:39 PM

Re: 1996 2.3 Engine Bucking under load
There's still a misfire at idle, and it has stalled at idle on occasion; It's not very noticeable unless you have your hand on the shifter. Another thing to note is the PS Pump seems to go back and forth noise-wise which tells me that the RPMs are fluctuating. (I can't hear the engine over the pump unless I'm standing with my ear to muffler)

casey.mikl 01-01-2016 03:12 PM

Egr will go bad out of no where that's what happened to mine. Idle ran terrible, would barely run. Only if we're on the gas.

MasterJax 01-04-2016 02:58 PM

Re: 1996 2.3 Engine Bucking under load
The idle isn't rough or anything, it just has a very light weight misfire that turns into bucking at higher rpms.

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