4.7L stroker OBD1 codes/tuning

[MasonMcK]

Hi guys, I got my 4.7L stroker fired up for the first time 3 days ago. I have been fighting off various issues since then but I have almost all of them figured out. My current issue is my engine runs perfectly fine, but will throw a code when I'm just barely starting to push on it a little hard. If I drive really slowly and easily I don't get the code, but if I push on it slightly harder than normal driving it will throw the code. How hard do you have to be pushing on it to get it to go into open loop mode? My Cherokee is a 1995 so it has OBD1. The code it's been throwing is #21 which translates to:

-(Upstream oxygen sensor response slower than minimum required switching frequency.)

-(Upstream oxygen sensor heating element circuit malfunction)

-(Downstream oxygen sensor heating element circuit malfunction)

-(Downstream oxygen sensor input voltage maintained above the normal operating range)

-(Oxygen sensor voltage too low, tested after cold start)

-({Upstream or downstream} left oxygen sensor input voltage maintained above the normal operating temperature)

Considering my jeep is a 95 and didn't come with a downstream O2, that would rule those codes out correct? My upstream O2 sensor didn't get damaged during installation either. So my current thinking is my engine is running too rich or too lean, but shouldn't that be kept at 14.7 by the computer in closed loop mode? I'm not quite convinced yet that I was even pushing it hard enough to get it into open loop. But I've been wrong before. I am running a Hesco adjustable FPR set at 44psi, Bosch 30 lb/hr EV1 injectors, 62mm TB, stock 1995 fuel rail, and a stock 1995 fuel pump. I guess my overall question is: how hard do you have to push it to go into open loop? If it wasn't in open loop, how do I fix my rich/lean condition if the computer isn't maintaining it? And if it was in open loop mode, then I just need to make a MAP sensor adjuster and play with the voltage to get it to run as it should?

Thanks for the help.

[jsawduste]

Open loop comes in when the engine coolant temp and O2 sensor come up to temp.

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30 lb injectors at 44 psi ?

Your gagging that engine with fuel. Suspecting your codes may be coming from an O2 sensor that is asking the ECM to pull fuel and the ECM is saying I`m doing the best I can.

Most of us are running 24 lbers at around 42 psi +/- That seems to be a pretty good starting point.

Really would suggest you change the injectors and adjust the FP lower. Then see how it runs.

[Cheromaniac]

Agree with John. Those 30lb injectors are way too big and the ECU cannot reduce their duty cycle far enough to compensate. I suggest you run Ford blue top EV1 24lb injectors with the stock 39psi fuel pressure regulator.

[jsawduste]

Thanks Dino.
Lets hope the OP works out his issues and reports back.

[MasonMcK]

Thanks for the replies guys. I had the 30lb'ers on hand so I threw them in for now hoping it would be able to compensate. I'm building a MAP sensor adjuster this coming weekend. Do you think the MAP adjuster will be able to tune it to run right on the 30lb'ers? If not I'll bite the bullet and go with a set of 24lb injectors.

Thanks,
-Mason

[SkylinesSuck]

I don't think a MAP adjuster will be able to cut it. Get the right injectors.

[jsawduste]

MAP adjuster will only work in open loop.

IE 75% or higher throttle on a warm engine.

[Cheromaniac]

Do you think the MAP adjuster will be able to tune it to run right on the 30lb'ers? If not I'll bite the bullet and go with a set of 24lb injectors.

In a word, no. Get the 24lb injectors.
As John correctly mentioned, the MAP adjuster only makes a difference when the engine's ECU is in open loop mode (heavy acceleration with 70+% throttle, cold start, deceleration).

[MasonMcK]

I really appreciate you guys clarifying things for me. What about the adjustable fuel pressure regulator? Can I just crank down the pressure of the fuel rail to get it to run right or does it need the higher pressure for better atomization? If not will that work as a temporary fix (about a week) until the 24lb injectors arrive? I can't find any with shipping sooner than a week and I need to be able to drive it in the mean time. Also on the topic of injectors, what injectors do you recommend I run? I heard mention of the Ford blue top injectors. Are they narrow or wide body injectors or does it matter? Are the narrow ones actually any better than the wide ones? My jeep is a 1995 so it uses the EV1 connector. The ones I have now are Bosch 30lb/hr narrow body injectors with the EV1 connectors. Thanks for all the help.

[jsawduste]

summit racing
accel 24 lbers set of 6.
order by 5pm and they show up next day.

No, you don't want to turn the FPR down. Couple lbs ok but not much more.

I`d be more worried about washing the cylinder walls down with raw fuel running the way you are now..

[MasonMcK]

The new 24 lb injectors are set to arrive on Tuesday. I will post back on how everything goes. I don't have a wideband O2 sensor yet nor do I have the funds currently to buy one. Can I read voltage off of the O2 sensor to determine how I need to adjust my pressure regulator or is that only during open loop mode? If not what would be a ball park range that I should set my fuel pressure regulator to for safe running? I will eventually get a wide band O2 but not for a couple months.

Thanks again
-Mason

[Cheromaniac]

Set it at 44psi for the Accel injectors. It should be pretty close and you can work from there.

[jsawduste]

Dino

[Russ Pottenger]

Do we have part numbers for the Accel injectors?

[MasonMcK]

Thanks for all of the help guys. I'll post back on Tuesday and give an update on how everything goes. The injectors I ordered are Accel part number: 150624. They come as a set of 6. They also sell them individually or in 8 packs. I also have a fuel pressure gauge in the mail so I can dial my pressure in accurately.

Thanks!
-Mason