My friend has a 1988 F-100 with a 4.9

We have looked for the knock sensor and can't seem to find it. Did the '88 come with a knock sensor? If so, could someone explain where it is. I hope someone can help.

Thank you,
Brandon

 

First-There is no F100 in 1988 there is a F150?
Second- To my knowledge no 4.9 came with a knock sensor. Someone can tell you differently. But I know of none.

 

My 1991 4.9 has a detonation sensor. It's unplugged because I was having erratic timing issues that went away by unplugging it. It's is on the lifter cover side of the engine near the front. Basically tucked up directly underneath the TFI ignition coil, sticking out of the block with an electric plug in it. It's a little larger than an oil pressure switch. Don't know about a 1988 though.

 

There be a better awnser.

 

Sorry, I meant F-150, not F-100.
Thanks for the responses so far.
So does anyone know for sure if they had detonation sensors in 1988 on the 4.9s?

Brandon

 

I have a pic of the one on my '89...lemme see if I can find it...



Oh, yeah...took that pic a while ago, but I think my hand is on the distributor...of course, we still haven't answered the question on whether the '88 4.9 got the knock sensor, but we're getting closer!

Pat

 

NAPA lists echlin pn-ECH DKS205 @ $114,as a knock sensor for an 88 F150 4.9.

 

Thanks for the picture. If Napa shows one, I'll check and see if the sensor is in the same place as it is on your '89.

Brandon

 

I found this on NAPA's web site. its for the 5.0 V8 but it looks "exactly" like the one on my 91 I-6. can anyone confirm its the same part?

Store Locator | NAPA Online

 

The sensors I have seen appear to all be the same. However, I have not seen many from other models in years. I currently have two trucks with 4.9L's and they are the same. One is a '90 and the other is a '95. I have the same problem with the '90 and swapped sensors. This did not change the issue. I think the sensors are all the same internally as they all do the exact function as the next. I would venture to say if the threads are the same and the harness works, then it is the same. When I connect the '90 to the scanner it consistently reads (no knock signal) even with the other sensor that seems to work just fine in the other truck. I have checked for vacuum leaks and changed the TPS and the TFI module in desperation as these are common failure components in fords. I have not had any luck thus far. I feel like this problem may be caused by a break in the wiring that is obviously rather common possibly due to heat, vibration and/or excessive pressure pulling on the harness somewhere. You may not need the sensor at all. The '90 has 348K on it with no mechanical issues what so ever. The valve cover hasn't ever been off. The '95 only has 198K but I fear it may soon fall in to this same problem. The only other thing I could imagine that could possibly have any effect on the scanner code would be the ECM. I am not sure what all diagnostics you have run. It would be best to check as far in depth as you can before spending money on replacing components that may not be bad as parts for this engine are getting harder to find since it is not considered a performance engine. I have read several posts that date back as far as 2003 and have not found any confirmed fix for this problem. These are one of the best engines produced in their era, but it seems like technology has now stopped so many of these workhorses. I will continue try to find the cause.

 

I have finally fixed the problem hiding behind the (no knock signal) code I have been getting from my 1990 F-250 300-6. It was simply corrosion in the distributor. I just pulled the distributor and cleaned the bottom side of the steel cap below the rotor button and any connection between metal surfaces including the base of the distributor and the retaining bolt. Before reassembly I coated all contact points with electrical joint compound which is basically a corrosion inhibitor similar to grease enriched with fine copper grindings to ensure conductivity. Proper electrical connection is the key with low voltage connections, especially in the automotive application, were extreme temperatures, moisture, and corrosive materials affect the wiring. Cleaning the components below the rotor button can can be performed without removing the distributor. It would be much more simple than removing everything and may fix the problem. If it doesn't then remove the distributor and clean everything. I mean cleaner than hospital clean. Corrosion=resistance=voltage drop. When you only have 12V to begin with, nearly any voltage drop is to much. I think the code was given because the ECM of that era was not as elaborate as today's model's and that was the only code it could produce with the information it gathered.

 

Did you ever figure out why you were having the erratic timing issues? I've replaced the sensor you speak of, tps, egr sensor, idle air sensor and valve, cap, rotar, vacuum lines including the vacuum solenoids by the 5th and 6th spark plug back, and map. Even other things not directly associated with the issue like speedometer sensor, oil pressure sensor, and vacuum canister. But have a tendency to through the domino effect that is mechanical failure. Cause such behavior. Also while im here. How much does the smog system affect the overall running of the engine. Ive heard none ive also heard that the added inert gasses causes the computer to change air and fuel ratios. I ask because there has been exhaust work done and the pump doesn't run to anything anymore.

 

What is your specific issue Mr Yates?

You kind of ask a ton of different questions. You can yank 90% of the smog off of this era and they run fine.

 

I am also having erratic timing issues. Unplugging the sensor that most have been referring to as the knock sensor clears it up to where the miss is almost non-existent. All the parts listed in previous post are what I've replaced. With sensor plugged in. When i first start the truck it idles high as most do from initial start up. Runs smooth. Drops rpm to its normal operating idle. At this point sometimes itll idle for a bit sometimes it will immediately start to choke. The length of time is never the same. Then like i said it chokes like u pulled a main vacuum line. Idles down rough like it wants to die. Im assuming at this point the sensor is adjusting timing and it idles up fairly high stays there for a moment and slowly drops back down to regular idle. Theres a intermittent "puh" sound. Like when enunciating the letter P. Then it repeats the process all over again. Almost dying then smoothing out almost dying smoothing out on and on no matter the temperature. Its not a until it warms up thing its not a once its warmed up thing. The amount of time it idles good after initial start is never the same and the amount of time it struggles to idle correctly is sometimes short and sometimes it takes it a minute. The time it runs smooth after its little fit is almost always different also. Im perplexed to say the least and about ready to be done with it all together.

 

I am assuming your spout connecter is in.

Kind of sounds like a bad map sensor or bad injectors to me. This vehicle is 32 years old,

The high low idle thing (swinging RPM) is pretty common on OBD1 ford trucks. I do not know why.